Product FeaturesProduct Name : Linear Bearing;Model : LMK12UU;Material : Metal, RubberInner Diameter : 12mm/ 0.47 inch;Outer Diameter : 21mm/ 0.82 inch;Length : 30mm/ 1.2 inchSquare Size : 31 x 31 x 5mm/ 1.2 inch x 1.2 inch x 0.2 inch(L x W x T);Mount Hole Dia.(Each) : 4mm/ 0.16 inchHole Pitch : 21mm/ 0.83 inch(Center to Center);Color : Silver Tone, Black,Net Weight : 220g;The universal Ball Bearings is great for you to replace the damaged Ball Bearings in your devices to improve them efficiency and save energy.Widely used in home appliances, industrial, low noise and high speed electric motors, construction machinery, automotive components, pumps, and machinery.Smooth moving, low friction, high rigidity and long life.Economical, easy to maintain replace.Package Content : 4 x Linear BearingOnly 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.