4pcs LM20UUOP 20mm open type Linear Ball Bearing Bush Bushing 20*32*42mm for DIA. 20mm linear shaft rod DIY CNC OPEN TYPE Linear bearing ball cage, hardened coat of both ends ring. Bearing various parts of the size is standardized, interchangeable, no worry if replacement of worn Ball in the cage loop to run a smooth ball guide surface to ensure. Size : 20*32*42mm Color : silver OPEN TYPE