About this 3D model

**Improvements:** - The axial forces are supported by the rollers in place of the housing. - Stronger housing (1.5 instead of 1 mm and inner facets). - Another 4 mm wheels. **TODO:** - The rolls have 2x0.1 mm axial play, maybe 2x0.05 would be better. - There are also less clearance between the outer and the inner race than the rollers have in radial direction...)