If you’re assembling V-wheel setups on V-Slot or V-Rail systems (for 3D printers, CNC, etc.), you’ll have noticed the bearings sitting tightly on the shaft; without precise spacing, they can bind or wear prematurely. These little shims do exactly that job. They’re thin stainless-steel precision spacers inserted between the two bearings or between the bearing and wheel/housing to keep everything aligned just right. For a low cost, you prevent binding, reduce friction, keep smoother motion, and help your wheels last longer.