Suitalbe for CNC machine electronic equipment,drive shaft, and etc. Colour:silver Material:Metal Size:Inner diamter: 16mm ( LM16UUOP) Package Contents: 4 x SBR16UU Linear Ball Bearing Slide Block Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.