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Article: BSUN Bunny Linear: Review by Vere

BSUN Bunny Linear: Review by Vere

BSUN Bunny Linear: Review by Vere

Opening words:

Hello, this is Vere. 

I am a member of the Unikeys discord and I am usually around to discuss switches and other custom keyboard related topics. 

I started writing switch reviews on the discord for fun, but people seemed to genuinely enjoy them. I was really humbled when Dashan reached out to me and asked if I wanted to post any reviews on the site and I gladly accepted.

This will be my first official review and I made it a bit more in-depth on purpose. I simply hope that these reviews will be helpful to those who are a part of this hobby and share an interest in switches like I do. 

Everyone is entitled to their own opinion and I myself am not perfect when it comes to switches, please read this review with that in mind. There is a mix of my personal knowledge, but also information that I’ve tried to find online regarding other topics.

I will try to write these reviews for interesting switches every so often.

Switch Introduction: 

The BSUN Bunny is a long pole linear with a transparent polycarbonate top housing, lilac-colored modified PA(Polyamide) bottom housing, and pink modified LY stem with UPE added. It carries a 22mm single-stage spring with operating force of 37g and bottoming out at 42g. The total travel distance is 3.6mm.

These switches were manufactured by BSUN but designed by KeysU Studio in China. 

These switches are different from most of BSUN’s other LY offerings due to the modifications made to the components which allow it to stand out when compared to the many other BSUN LY switches.


Short Summary


Moderate to High, slightly louder than some other long poles.


Higher-pitched and slightly thin due to LY

Sound Profile

Clean and resonant bottom out, no audible scratch from travel.


Good lube coverage. Relubing is optional and can offer minor improvements to some spring/leaf noise. Good wobble control.


Pretty colors that would match a lavender board nicely.

I suppose most Bunny motifs are a similar color.


Modified materials, strays from the usual BSUN formula.

Stock Experience: 

The BSUN Bunny uses BSUN’s standard factory lubing technique which uses a mix of Krytox 205g2 and GPL 105 (popular combo in the east) in a ratio of 7:3 which allows for a smooth travel without deepening the sound profile too much. The lube is applied on the bottom housing railings and the stem has dry film lube applied to the stem and spring.

The lubing was quite consistent and there was a decent amount on each switch, adding any more on top of the factory lube would deepen the sound quite a lot in my experience.

The BSUN Bunny is perfectly usable stock, BUT a few switches in my batch had some under-lubed switches/springs.

I felt that the Bunny’s stock form is on par with most of the other BSUN switches. The wobble is also well controlled and I don’t believe these switches would benefit from films.

What exactly is LY?: 

LY is a proprietary material blend that was first introduced by JWK and BSUN, one of the first notable switches that used this material were the SOTC switches, manufactured by JWK to pair with the Glacier80 from CreateKeebs. 

Apparently, the material itself is made up of several different plastics, but is mostly made up of POM + UPE, or POM + PTFE 

(based on a comment from GEON, from MakerMods’ video on Wikuo Harmony Linears). 

What are these fancy names you ask? On a basic level, PTFE and UPE are types of polyethylene plastics that have extremely low coefficients of friction and are soft, yet are resistant to wear and abrasion. (UHMWPE is a polyethylene plastic btw)

I cannot confidently say if the LY used by JWK or BSUN is the same, but they share similar qualities. Smooth and high-pitched.

The coefficient of friction of LY is 0.3, if the number of the coefficient is closer to 1.0, then the stronger the stick-slip resistance

In short, lower is better, but if two materials share the same exact coefficient of friction, binding will occur, where the materials can possibly start combining. This can also be referred to as adhesion, but usually you don't see it these days since manufacturers have wizened up.

Just for a point of reference, your average Nylon has a coefficient of friction ranging from 0.5 to 0.7, while POM ranges from 0.25 to 0.3. 

LY is essentially a smooth material created by blending the tried and true POM(Stiff, low friction) material with softer plastics that have a low coefficient of friction without compromising stability.


The hunt for smoothness: Making your own material

So why go through the trouble of making your own proprietary material? First, marketing and business of course, capitalism at its finest. After all, who wouldn’t want to buy switches with special mystery materials that are apparently exclusive and unique? In most cases, this is probably why many manufacturers never go into specifics on how exactly they modified their materials or what these code names even mean.

It’s still a competition at the end of the day. 

The second reason is the limitation of materials that are actually usable for switches, as they need to fall within a specific frame of traits that are viable for production. Low enough coefficients of friction, able to withstand countless actuations, able to be molded into specific forms while retaining structural integrity. Not only that, but many plastics are susceptible to varying degrees of shrinkage in the process of creation. This led to manufacturers cooking up their own blends of materials to match their needs rather than using what is on the market.

That being said, it wasn’t a very smooth path to making successful materials. When looking back on the past, there are definitely a few examples of switches out there that had problems arise when manufacturers experimented with different materials .

I won’t go over them all, and I’m sure there’s some that I am unaware of, but here are some examples.

Tecsee: PME, which was one of their first proprietary blends, had flaking issues, where the plastic itself had flakes of itself fall off from actual use. (Didn’t affect much unless many flakes entered the center pole).


UHMWPE: When first playing around with UHMWPE there were cases of the switches that used UHMWPE literally breaking apart due to being too brittle for proper use. UHMWPE is a polyethylene so it has a very low coefficient of friction, and is in fact a resistant plastic, but nowhere near as resistant as Nylon, POM, or Polycarbonate, etc. (This is why we now have LY, HPE, and a few other UHMWPE proprietary blends.)


PBT: Yes, PBT, the plastic that you probably know is popularly used for keycaps was also tested with for switches.

PBT is one of the plastics very susceptible to shrinkage so it’s a nightmare to work with for manufacturers. There are very few cases of successful switches with PBT included in the housing and you can probably count them on one hand. 

(Meirun has been behind most of the usable PBT switches, Meirun is pretty awesome when they get it done right.)


Modifications to the LY Stem:

When referring to modifications, this usually means that a different plastic or material has been added to the original base material in order to strengthen or change its properties. 

Blends are not the same, blends combine different types or forms of the same plastic family in order to try and create a different result. (e.g. Blended Nylon or Blended POM).

When manufacturers are trying to create different blends or modifications, you can tell they are trying to reach a very specific type of material for the switch. (In hardness for sound, or perhaps smoothness for feel) This is usually a good thing, as it means that a simple Nylon housing + POM stem switch might actually be more interesting than you would expect.

If you read above earlier then you would notice that LY is POM + UPE, so that means… the BSUN Bunny just has more UPE added to the stem?

Well that depends, I’m not privy to the secret formula of LY but adding more of a softer plastic would definitely reduce the hardness of the original POM stem, leading to a softer bottom out, and adding a soft material such as UPE would also dampen the sound.

This would explain why the bottom out of the BSUN Bunny feels and sounds different compared to the other BSUN LY switches.

An important issue, or a quirk, with the LY stem: 

I ended up making a shocking discovery only recently before writing this review, which is part of the reason why I wanted to discuss this switch more than some other BSUNs. 

Like I mentioned above, the modified LY stem contains more UPE than your average LY stem, and this comes at a possible cost of losing durability and dimensional stability. 

I was able to experience this firsthand as I had opened up a few switches with my Gateron Switch opener to re-lube them… but they suddenly changed drastically. Not only in sound but feel too, 

I thought it was bizarre when I had only lubed the springs and leaf slightly, then when I thought long and hard about the possibility, I realized that opening the switch itself may have changed something. 

I went back to open up the switches I re-lubed and couldn’t find anything EXCEPT, the stem pole was slightly compressed at the tip, almost like it was flattened. I realized now that the LY+UPE stem is actually too soft to handle certain amounts of pressure, specifically a metal Gateron Switch opener which is almost like a nutcracker. When I compared the compressed stems with the stock stems, they were noticeably different, and you can even clearly tell that one is kind of altered. 

I also noticed that the travel of the switch went from 3.6mm to 3.7mm, which would obviously change the feel. 


(Left stem was “compressed”, right stem is stock)

So why would I say that this is a quirk?

The answer to that is simple, I actually like the way they sound and feel AFTER the stem pole is compressed.

The notable differences are a softer and deeper bottom out, and the increased travel is my preference because I am getting tired of long poles. Thanks to the compression of the pole, the stem is slightly flatter and has a larger surface area compared to the thin tip of the pole. Generally thin elongated tips will lead to a sharpness in the bottom out with less surface area, while flatter and rounder poles will lead to a more balanced sound. In stock form, the Bunny does have the iconic BSUN clack to it, but post compression these switches become even gentler than I had expected.
Now, this is ultimately a quirk because this is an "optional" change. You can avoid this issue by simply opening with any smaller metal switch opener, such as the ai03 switch opener, or the Geon Switch opener if you would rather keep the sharpness of the switch, but if you wanted to dampen the sound and try to make it softer, then I recommend compressing the stem slightly. (I know it's still hard to call it optional, when most people would be unaware)

Keep in mind that regardless of the force I exerted, the switch would not open unless I used a specific amount to overcome the housing tolerance, and it was enough to alter the stem. The result was the same 5 out of 5 times when using the Gateron Opener.

In short, overly soft materials are prone to being malleable or alterable, worst case scenarios being damaged or even broken.

This is likely the reason why some switches that have UPE materials have many inconsistencies, perhaps even from daily usage.

Modifications to the PA Bottom:

I went through a bit of a plastics study session for this review.

Now here is a simple explanation behind the many names of the thermoplastic commonly known as Nylon. 

First of all, Polyamides that have numbers attached are actually quite different from Polyamide Compounds(PA). 

The numbers attached to the different Polyamides refers to the number of atoms inside their monomers, for example PA66 is actually Polyamide 6,6 which refers to it having 6 carbon atoms inside its two monomers. 

You can correlate the atoms with the strength of the compound itself, PA12 for example is actually PA 1,2 and not actually 12 atoms, but rather 1 and 2 atoms in the monomers. PA6 being a singular monomer of 6 atoms. (Tecsee’s plastic of the apocalypse PA666 may or may not follow this rule, it's a proprietary name)

This should give an idea about the strength and stiffness of the different nylons, which should correlate to their sound properties.

From lower to higher pitch: (Estimated guess)
PA1 -> PA12 -> PA2 -> PA6 -> PA66 -> PA666 -> PA

These Polyamides are known as Aliphatic Polyamides. (Nylon)

Nylon is commonly used for switches thanks to being cheap and easily accessible, resistant, having high flexibility in use, as well as having a lower coefficient of friction than other plastics. 

So what is PA then?

PA or Aromatic Polyamide, or aramid, or most commonly known by the trade name Kevlar, is chemically a much stronger compound of polyamide compared to Nylon. 

It has higher strength, chemical, and heat resistance, and better dimensional stability than Nylon, it is commonly used for helmets, bulletproof vests, reinforced plastic piping and jet engine inlets. 


Despite using a softer stem, the BSUN Bunny is able to retain its clacky sound signature using a strengthened PA bottom which is stiffer and chemically stronger than your average nylon. This means it is capable of producing a louder sound and it will lean towards the higher pitch due to having a higher stiffness than nylon. There isn’t a massive difference in density between the two, so the main factor for sound is stiffness. (Softer materials are better at absorbing frequencies and will tend to reduce volume and pitch, while stiffer materials are not good at dispersing frequencies and will increase volume and pitch)

(From Keybored’s video on sound in keyboards)

Sound Profile: 

Due to being a long-pole, these switches have a moderate-to-high volume and lean towards the higher pitch when discussing sound profile. 

Most LY stems sound similar due to the polyethylene material leaning towards a specific sound profile, but thanks to the modification made to the bottom polyamide(PA) housing, these switches are able to keep a lively sound profile while still being very soft on the bottom out.

However, after the stem pole is compressed, these are slightly quieter and deeper, becoming closer to the moderate volume when compared to other long poles, and pitch also lowering from high to medium-high.


Direct Comparison to other Linears:

Blue Balloon, Roselle, Macaron

BSUN Roselle (POM/POM/Y3 Stem) 3.6mm Travel

  • While these switches share the same manufacturer, the material composition differs considerably and the sound profiles that result are expected.
  • The BSUN Bunny ended up having a gentler sound than the Roselle’s material structure of POM + Y3. Likely the Y3 material has some more sharpness to it while retaining smoothness, POM housings are deep but can be loud.
  • The Roselles are slightly smoother than the Bunnies. The Roselles are noisier than the Bunnies thanks to their audible scratch and also the sound profile is more full and less compressed on the bottom out.
  • They both have excellent stem wobble control and stock quality.
  • They share the same travel distance, but the Roselle has a slightly firmer bottom out and lower pitch.

HMX Macaron (PC/Modified Nylon/POK Stem) 3.6mm Travel

  • With the exception of stems, these switches are similar in material composition and are almost similar in sound. They both have excellent stock experiences, but the HMX Macaron uses a lot less lube and their choice of lubricant is oil based.
  • The Macarons are slightly smoother than the Bunnies. The POK stem of the Macarons lead to a more compressed and slightly thinner tone compared to the LY stem. 
  • The Macarons have slightly better stem wobble control and stock quality.
  • They share the same travel distance, but the Macarons have a firmer bottom out. (Polyketone seems to be less firm than POM, but firmer than LY at least) These switches both share a higher pitched tone with medium-high volume. 


Tecsee Blue Balloon v2 (PC/Nylon/POM Stem) 3.5mm Travel

  • With the exception of stems, and slightly different bottoms, these switches share similar materials and differ in sound. The LY stem of the Bunny leans towards a thinner and higher-pitched sound. Meanwhile the traditional POM stem of the Blue Balloon leads to a full medium-high toned sound profile. 
  • The stock form of the Blue Balloon cannot compare to the Bunny considering there is no lube on these switches. The housings require films to prevent housing noises and wobble. There is a lot of leaf noise and spring crunch.
  • When fully lubed and filmed, the Blue Balloons can match the stock form of the Bunnies in smoothness, however this is up to you as the consumer if you believe the effort is worth it.
  • The Blue Balloons have a shorter travel by 0.1mm, and have a firmer bottom out. These switches are deeper than the Bunny when lubed, and have a full and resonant sound profile that isn’t compressed.


Before wrapping up, I can’t be biased and only go over what I like about the switch. 

First let’s talk about the inevitable flaw with BSUN’s lubing process. Due to using a mix of lubricant using a grease (205g2) and oil (105), eventually these two will separate from each other while inside the switch (aka decantation). This can be noticed in other BSUN switches that eventually have the oil lubricant pooling at the bottom of the housing (i.e. Owlab London Fog). Temperature may play a large factor in the speed at which this occurs.


Another possible “flaw” to some would be the extremely light bottom out weight at 42g as this slightly interferes with the design thesis of this switch being a soft daily driver. With such a light spring, it is incredibly easy to bottom out on these switches regardless of whether you are a light or heavy typist. 

Even if the switch is meant to be “soft”, if you type hard then it’s easy to get some sharp bottom outs.


Notably, I realized that while these switches are excellent, they do not use the smoothest options available as the main intent behind these switches is to retain a strong sound whilst being soft. As such, using a PC top and PA bottom doesn’t generate the same results as using POM or POK housings. BSUN’s factory lube isn't perfect in my personal opinion, so these switches might not be “smooth enough” for the most sensitive users out there. (This is an extreme case as they are still very smooth)


Lastly, I mentioned earlier in the review, but if you use a strong switch opener like the Gateron Switch opener, you will most likely compress the very soft LY+UPE stem into an altered state. This means that you will irreparably change the sound and feel of the switch. If you are fine with this change and don’t consider it a major flaw, then you can think of it as a quirk. I personally do enjoy how it sounds after compression.

Personal Build Recommendation:

(This section is entirely opinion/preference based, so please take it with a grain of salt.)

With the specific traits of this switch, I would recommend using it on a stiffer plate with an optional fuller/resonant mounting style.
For example: Aluminum Top Mount or Carbon Fiber O-Ring, or perhaps the best of both worlds: Aluminum Gasket.

It is a long pole with softer materials, which means it won’t be harsh to bottom out and you can make use of the livelier sound, especially on metal plates.

Due to the nature of LY leaning towards a specific sound profile and being muted, I would avoid using this switch in plastic plates on Gasket Mount, as I feel that the sound would be too dampened and this switch would lose most of its character, however if you are trying to attain an extremely soft/comfy typing experience then something like Polycarbonate/PP Gasket Mount would be ideal. 

I have also tried these switches in plate-less configuration and they are pleasantly gentle to type on, but I prefer the sound of something like Aluminum/FR4/Carbon Fiber with these.


Closing Summary:

To keep it short, KeysU Studio hit the nail on the head with their goal, an addicting daily driver switch that won’t exhaust your fingers. By carefully adjusting BSUN’s formula, they were able to tune this switch into a clacky yet soft option which contrasts many of their more harsh bottom outs. (SSW, Aniya, etc.)

At the price point of 46 cents per switch, it’s hard to pass up this excellent stock experience and quality. Though there are a few things that disappointed me, I still think these switches rank high when compared to most of the long poles out there these days.

If you are in the market for an aesthetically beautiful switch with a clean and pleasant sound profile that gently cushions your fingers like petting a soft Bunny, then you should consider checking these out. I would rank these very high on the BSUN tier list, and the quirk with the stem makes these a little more interesting to me.

Final Scoring: 7.6/10

Design: 9/10 

[The goal was a long pole with a soft bottom out that won’t fatigue your fingers after long periods of use, I would say that’s been achieved here.]

Sound Profile: 8/10 

[Strong sound profile despite the usage of LY, the modifications have made this switch stand out amongst other BSUNs in terms of unique sound.]

Stock Experience: 7/10

[Minor spring ping and leaf noise is audible from a few switches, not the best compared to other stock BSUN, but still excellent compared to most manufacturers.]

Uniqueness: 9/10

[Modifications made to the switch have made it more unique than the other generic BSUNs, and the way the stem can be “altered” does make this switch slightly more interesting in the long run.]

Flaws: 5/10 

[I have to dock points due to the stem being so easily malleable, and can possibly be damaged from long time use, this is ultimately a flaw.]

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