These pulleys are commonly used components in coil winding machines and textile machines in instances where there are radical changes in the direction of a passing material (such as copper ramic roller rings are made of fine ceramic (Alumina Al2O3), with a hardness of HRA88, density of 3.85 and the surface polished to ultra-fine Ra0.2 finish. It has a high-speed precision bearing within the ceramic roller ring, which keeps the sliding distance between the enameled oll.