Durable orange polyurethane. Will not mark or discolor boat. Cut and abrasion resistant. Will not "flat spot" even after months of storage. Roller is unaffected by grease, oil, gasoline, exhaust fumes, salt, etc. No bushings to pop out. Continuous bearings and reinforcing tubes on rollers over 7" long are completely enclosed in polyurethane. Shafts should be greased at installation.