Black 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. Sheave Ø (mm) 57 mm Sheave Ø (in) 2 1/4 in Length (mm) 119 mm Length (in) 4 11/16 in Weight (g) 152 g Weight (oz) 5.36 oz Shackle pin Ø (mm) 6 mm Shackle pin Ø (in) 1/4 in Maximum line Ø (mm) 12 mm Maximum line Ø (in) 7/16 in Maximum working load (kg) 1134 kg Maximum working load (lb) 2500 lb Breaking load (kg) 2268 kg Breaking load (lb) 5000 lb