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. Bearings may require lubrication and break in period. Great for linear motion on 3D printer, cnc, and other applications. Smooth moving, low friction, high rigidity and . Economical, easy to maintain replace., Weight: 0.436956203284 pounds, Manufacturer: HuddleGlow