This sheave has the same profile as the polished groove aluminum sheave but has a cast-in-place polymer urethane with 90-92 “A” scale durometer hardness. S+R Urethane is a polymer with a special kind of thermo-setting characteristic. It combines in one material the resiliency of rubber and the hardness of structural plastics and possesses the additional important properties such as high load bearing capacities, resistance to impact, abrasion, compression set, ozone, oil, and many chemicals. Due to its elasticity, the material will flow under the load exerted by wire rope pulling line or conductor, making it an ideal application for conductor, static wire, or even fiber optic cables. Interchangeable with all XS-100 frames.