This 12mm x 21mm linear bearing is built to run on our 12mm stainless steel shafting. The internal carriage contains a series of balls that cycle through as the bearing traverses up and down the shaft it’s installed on to provide a low coefficient of friction. The seals at each end keep ingress of dust and debris to a minimum for long-service life. These bearings can be mounted with one of our 21mm bore clamping mounts. The added length of this unit, when compared to the 1612-1221-0030 provides greater load capacity and more stability.