Harken Micro Blocks Low-friction Micro blocks are compact and lightweight, with fast trim and release under high or low loads. Ideal for sailboards, smaller dinghies, and for lightly loaded control lines on boats of all sizes. Free-rolling Delrin® ball bearings, sheave and sideplates UV-stabilized, with carbon-black additive for maximum protection. Stainless steel sideplates for strength. Use for: Cunninghams/outhauls Vangs Traveler controls Barberhaulers Flag halyards Leech cords Lead car return tackles