Kasm is a 3D printed slimline return top designed for modern responsive (0A) play.
Bearing: Size B
Response: Flowable silicone (or Freehand pads)
It uses a small bearing, but also comes with "bearing locks" (red ring in the last picture). Putting one of those rings into the bearing seat will cause the bearing to lock up, using the outer race of the bearing itself as a fixed axle.