Harken 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 AirBlock® 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 ride on high-load composite bearings. They are Hardkote-anodized aluminum with Teflon® impregnation. Ball bearings in the 11/2 in (38 mm) and 2 in (51 mm) sheaves minimize friction. The 1 in (25 mm) wire sheave uses low-friction washers for this purpose. Two 160 sheaves make up the 161 dual sheave universal lead. Use this sheave to divert a line that must turn in either direction. Use Cruising ESP sheaves to handle high static loads from halyards and reef lines. Sheaves are carbon-black Delrin® for UV protection and turn on stainless steel spacers. Contained sideload ball bearings allow sheaves to spin freely when loads are released. Sheaves require a sideplate for the sideload balls to roll on.