Harken 57mm Black Magic Block, Double | For Sailing | by West Marine

Harken 57mm Black Magic® Double Block allows a 2:1 or 3:1 purchasing system. The entire line of Black Magic® Air Blocks® offer a sleek and polished look. Their unique performance engineering remains the staple of the Black Magic line of blocks. These strong, lightweight blocks feature free-rolling, high-load Torlon® roller bearings for a high strength-to-weight ratio. Used for dynamic high load sail controls including mainsheets, runners, halyards and spinnaker systems. Air blocks are easy to clean and service. They have few parts and no loose balls or rollers to misplace. Unlike blocks that are riveted, fasteners allow quick disassembly with a single hex wrench. Key Features Lightweight blocks with high-load Torlon® roller bearings for a high strength-to-weight ratio Ideal for sail controls including mainsheet, runner, halyard, and spinnaker systems Center cage keeps Torlon® roller bearings separated and parallel to reduce friction Sheaves have radiused edges to protect today's high-tech line Stainless steel swivel shackle Low-load blocks have red isolators Sheave Diameter: 2 1/4" (57 mm) Max. Line Diameter: 7/16" (12 mm) Max. Working Load (MWL): 2755 lb. (1250 kg) Breaking Load: 5510 lb. (2500 kg) Weight: 12.05 oz. (342 g) Length: 5 3/16" (132 mm) | Harken 57mm Black Magic Block, Double | For Sailing | by West Marine