Choose between the lighter 42g option and the firmer 48g option based on preferred keypress resistance.
Description
Who It's For
Sound Profile
Review Video
Quality Assurance
HMX Rain RBO Linear Switch
The HMX Rain Rail Bottom-Out is a five-pin linear switch with a scratchy feel from top to bottom. Its design pairs a rail bottom-out structure with a material combination selected to keep the keypress relaxed, controlled, and consistent through the full travel.
The top housing’s matte guide rails and updated stem-mold components are tuned to work together for a more uniform sandy texture. PA66 housing material with a small amount of fiberglass was selected after extensive testing for stability, while the POM-blend stem was chosen for its preferred textured surface and feel. In another way, you can say the Rain switch is the RBO version of the HMX Azalea linear switch.
Its factory lubrication is specially tuned for scratchy switches: the spring and stem receive a thin dry-film treatment, while the leaf and spring-contact area of the bottom housing are evenly lubricated to control metallic noise. Areas where lubrication is unnecessary are kept as dry as possible to preserve the intended feel.
The colorway draws from the misty, rain-washed palette of Jiangnan water towns and Huizhou-style architecture—an understated Chinese aesthetic of soft rain and light wind.
Specs:
| 1 quantity = 10 switches | |
| Switch Type | Five-Pin Linear, Rail Bottom-Out |
| Designer | Youth Studio |
| Manufacturer | HMX |
| Top Housing | PA66 |
| Stem | POM blend |
| Bottom Housing | PA66 |
| Operating Force | 42g / 48g |
| Bottom-out Force | 53g / 57g |
| Pre-travel | 2.0mm ± 0.2mm |
| Total Travel | 4.0mm ± 0.2mm |
| Spring | 20mm single-stage |
| Factory Lubed | Yes! Specially tuned dry lubrication for a uniform sandy feel and controlled noise. |
Rail Bottom-Out Design
A Linear Switch Built Around an Intentional Sandy Texture
The HMX Rain Rail Bottom-Out is a five-pin linear switch designed by Youth Studio and manufactured by HMX. Unlike a switch tuned only for maximum slickness, the Rain is intentionally described with a consistent scratchy or sandy feel through the full keypress.
Its rail bottom-out structure, matte guide rails and updated stem-mold components are intended to keep that texture uniform rather than uneven. The product page also describes the Rain as the rail-bottom-out counterpart to the HMX Azalea linear switch.
Specification Guide
Two Force Options with Full 4.0mm Travel
The Rain RBO is offered in two spring weights. Both use the same five-pin linear architecture, material set and 20mm single-stage spring specification.
The two variants finish at 53g or 57g at bottom-out.
This is the listed actuation distance before the switch registers a press.
The longer total travel supports the full-stroke character described on the product page.
Materials & Lubrication
Material and Lube Choices Preserve the Intended Texture
The confirmed specification uses PA66 for both housings and a POM-blend stem. UniKeys notes that the housing material includes a small amount of fiberglass, while the stem material was selected for its preferred textured surface and feel.
- Top housing: PA66.
- Stem: POM blend.
- Bottom housing: PA66.
- Spring and stem receive a thin dry-film treatment.
- The leaf and spring-contact area of the bottom housing are lubricated to control metallic noise.
- Areas that do not need lubrication are kept as dry as possible to preserve the intended sandy feel.
Sound, Feel & Build Fit
Who Is the HMX Rain RBO Most Likely to Suit?
The current page describes the Rain as high-pitched, clacky and crispy, with an intentionally scratchy long-travel linear feel. It is therefore a more specific choice than a conventional “ultra-smooth” linear switch.
May Suit
- Enthusiasts who deliberately enjoy a sandy or scratchy linear feel.
- Users looking for a high-pitched, clacky and crisp sound profile.
- Long-travel typing builds where a full 4.0mm stroke is preferred.
- Buyers choosing between medium 53g and 57g bottom-out weights.
May Not Suit
- Users who want the slickest, least-textured linear travel possible.
- Quiet offices or shared spaces where silent switches are a better fit.
- Anyone specifically looking for a deep, muted or thock-focused switch.
- Users who need a tactile bump or click mechanism.
Before You Order
Check Five-Pin Compatibility and Pack Quantity
One quantity contains 10 switches. The current product page identifies the Rain RBO as a five-pin linear switch, so the keyboard PCB and plate should be checked before ordering a complete set.
Choose either the 53g or 57g bottom-out variant, then calculate the number of 10-switch packs needed for the target layout. Actual sound will still change with the keyboard case, plate, mounting system, keycaps and internal dampening.
Ordering note: Each cart quantity equals 10 switches. Confirm five-pin support or the intended mounting method before purchasing for a full build.
Product Questions
HMX Rain Rail Bottom-Out Linear Switch FAQ
Is the HMX Rain RBO a linear switch?
Yes. It is a five-pin linear mechanical keyboard switch with a rail bottom-out structure.
Why does the product description call the feel scratchy or sandy?
That texture is intentional in this design. UniKeys describes matte guide rails, updated stem-mold components and the selected material combination as working together to create a more uniform sandy feel through the stroke.
What materials are used?
The confirmed specification lists PA66 for the top and bottom housings and a POM-blend stem. The product description also notes that the PA66 housing material includes a small amount of fiberglass.
What force options are available?
The page lists 42g and 48g operating-force options, paired with 53g and 57g bottom-out force variants.
What is the travel distance?
The Rain RBO is specified at 2.0 ± 0.2mm pre-travel and 4.0 ± 0.2mm total travel.
Is the HMX Rain RBO factory lubed?
Yes. The spring and stem receive a thin dry-film treatment, while the leaf and spring-contact area of the bottom housing are lubricated for metallic-noise control. Other areas are kept comparatively dry to preserve the intended texture.
What sound profile should I expect?
The current product page describes the Rain as high pitched, clacky, crispy and pleasant. Final sound will vary with the rest of the keyboard build.
How many switches are included per quantity?
Each quantity contains 10 switches. Order enough packs to cover the keyboard layout and any desired spares.
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Customer Reviews
Overall rating: 5.0 / 5 from 9 reviews.
These switches are really nice if you like that signature dry cherry scratch. For reference, I ran dry MX2A blacks with 60g springs, which I filmed and spring swapped myself. These feel a bit smoother than that but you can feel and hear the scratch in every key press. I think the 53g springs are bit too light for me, so I look forward to getting my hands on the 57g springs. Phenomenal performance for the price, and definitely a must-have if you like RBO switches.
HMX Rain Rail Bottom-Out Linear Switch Factory Lubed (10PCS)
Easily HMXs best RBO switch and their best scratchy switch in my opinion. They're very full and deep, with no unwanted noise like chatter or ticking. They're similar to MX Blacks but are different enough to have their own character. They are VERY scratchy in both sound and feel. This should go without saying but if you don't like scratch these switches are not for you. They have far more significant scratch than something like Lanikais but it feels more refined and less grainy than Sonjas, which are switches I do not like. If you like scratchy and/or RBO switches these are definitely worth trying out. They're my favorite HMX switches to date. Build in video is as follows: Bowl x Alexotos Manta, alu plate, o-ring mount, no foam, KKB celestial kinetics, HMX rain switches
HMX Rain Rail Bottom-Out Linear Switch Factory Lubed (10PCS)
These are really nice switches. Medium volume, a lower pitched clack than typical HMX switches - more similar to mx black. The scratch is beautiful.
HMX Rain Rail Bottom-Out Linear Switch Factory Lubed (10PCS)
Very nice to type on. Love full travel switches
HMX Rain Rail Bottom-Out Linear Switch Factory Lubed (10PCS)
sandpaper feeling on key press with a crisp dry sound on alu with CRP. These are my favorite non cherry RBO full travel.
HMX Rain Rail Bottom-Out Linear Switch Factory Lubed (10PCS)
Great switch overall. Below average spacebar switch.
HMX Rain Rail Bottom-Out Linear Switch Factory Lubed (10PCS)
HMX Rain slaps. full travel scratch goodness
HMX Rain Rail Bottom-Out Linear Switch Factory Lubed (10PCS)
The best switch in 2026 imo, if you prefer scratchy switch then this is the one.
HMX Rain Rail Bottom-Out Linear Switch Factory Lubed (10PCS)
I love these switches even though I just put them in my Tofu60 3.0 the other day. I believe they'd sound even better in one of my heavier boards. They are scratchier in both sound and feel than any of my other scratchies (Torreros, cherries, nezukos, purple sprout) in a really good, consistent kind of way. The clack also sounds somewhat deeper than the aforementioned.
HMX Rain Rail Bottom-Out Linear Switch Factory Lubed (10PCS)