Great for linear motion on 3D printer, cnc, and other applications. Bearings may require lubrication and break in period. These ball bearing with two rubber dust sealed to prevent ingress of dirt, water and foreign matter. Double Side Rubber Seal Linear Motion Ball Bearing Bushing. Smooth moving, low friction, high rigidity and . Economical, easy to maintain replace., Weight: 0.436956203284 Pounds, Manufacturer: Pomoflexi