Product Description Harken 100mm Aluminum Double Block w/ SwivelBlack Magic Air blocks are a top favorite of Big Boat performance racers and cruisers. These lightweight, free-running, powerful performers are used for sail controls that see lots of action: mainsheet, runner, halyard, and spinnaker systems. A center cage keeps Torlon roller bearings separated and parallel to reduce friction. Shackle blocks lock in two directions or swivel to keep line from twisting. Torlon is a registered trademark of Solvay Advanced Polymers L.L.C. Specifications: Sheave Ø (mm) 100 mm Sheave Ø (in) 3 15/16 in Length (mm) 227 mm Length (in) 8 15/16 in Weight (g) 1284 g Weight (oz) 45.28 oz Shackle pin Ø (mm) 12 mm Shackle pin Ø (in) 1/2 in Maximum line Ø (mm) 16 mm Maximum line Ø (in) 5/8 in Maximum working load (kg) 4990 kg Maximum working load (lb) 11000 lb Breaking load (kg) 9979 kg Breaking load (lb) 22000 lb