Double Side Rubber Seal Linear Motion Ball Bearing Bushing. Great for linear motion on 3D printer, cnc, and other applications. These ball bearing with two rubber dust sealed to prevent ingress of dirt, water and foreign matter. Bearings may require lubrication and break in period. Smooth moving, low friction, high rigidity and long life. Economical, easy to maintain replace. Product Name: Linear Bearing Material: Bearing Steel, Rubber Color: Silver Tone Weight: 788g Model: LM25UU Outside Diameter: 40mm Inside Diameter: 25mm Length: 59mm package content: 4 x Linear Bearing 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.