Product FeaturesProduct Name : Linear Bearing;Model : LMK12UU;Material : Metal, RubberInner Diameter : 12mm/ 0.47inch ;Outer Diameter : 21mm/ 0.82inch ;Length : 30mm/ 1.2inch Square Size : 31 x 31 x 5mm/ 1.2inch x 1.2inch x 0.2inch (L*W*T);Mount Hole Dia.(Each) : 4mm/ 0.16inch Hole Pitch : 21mm/ 0.83inch (Center to Center);Color : Silver Tone, Black,Net Weight : 55g;The common Ball Bearings is great for you to exchange the broken Ball Bearings on your instruments to improve them efficiency and save energy.Widely used in domestic appliances, industrial, low noise and high pace electrical motors, structure machinery, car components, pumps, and machinery.Smooth moving, low friction, excessive pressure and lengthy life.Economical, easy to maintain replace.Package Content : 1 x Linear BearingOnly the above kit content, other products are usually not included.Note: Light reflection and different displays may cause the color of the object within the photo a bit different from the genuine thing. The measurement allowed error is +/- 1-3cm.