30 Pieces Skateboard Bearings Ball Bearing Deep Groove Ball Bearing Double Rubber Bearings Sealed Bearing for Skateboards, Inline Skate, Roller Blade Skates, 8 mm x 22 mm x 7 mm (608RS): Amazon.com:
uxcell LM4UU Linear Ball Bearings 4mm Bore 8mm OD 12mm Length for CNC Machine 3D Printer 4pcs: Amazon.com: Industrial & Scientific