The Keygeek Butterfly linear switch is very unique in two aspects:
It comes with not just a spherical stem tip, there is also a spherical contact point in the bottom housing; During the keystroke, the spherical stem tip hits the spherical contact point to create a deep and thocky sound profile
The keygeek butterfly linear switch might be the best thocky sounding keygeek switch so far. After fine tuning the material blend and molding design, the Butterfly switches sound deeper, thockier, and noise free; There is no spring or leaf noises during typing.