Self-contained sheaves are designed for sailors to use in custom applications. The Micro, Bullet, and Big Bullet sheaves are Delrin with Delrin® ball bearings. They are scored for rope. 16 mm sheaves are Delrin and feature stainless ball bearings that ride in a grooved race. Midrange sheaves come in either Delrin or aluminum for wire. Wire sheaves are Hard Lube-anodized aluminum that rides on high-load composite bearings. Ball bearings in the 38 mm (1 1/2") and 51 mm (2") sheaves minimize friction. The 25 mm (1") wire sheave uses low-friction washers for this purpose. Two 160 sheaves make up the 161 dual-sheave universal lead.