Harken 22mm Fiddle Micro Block with V-Jam Cleat is great for building a vang purchase system.
Low-friction Micro Blocks are extremely lightweight, free-running and compact. Designed for any number of uses on dinghies and for lightly loaded control lines on boats of all sizes. Derlin ball bearings are UV stabilized with carbon black for maximum protection and stainless steel side plates add strength. Use inside masts, booms, lead car returns and tackle.
