57 mm Carbo Blocks Carbo AirBlocks® are 60% stronger and 30% lighter than our classic blocks. The nylon resin sideplates are densely packed with long-glass fibers for a compact block with a high strength-to-weight ratio. Ball bearings, sheave and sideplates UV stabilized with black additive for maximum protection. Blocks feature Cam-Lock or U-Lock locking systems to lock the shackle in front or side positions, or swivel to keep line from twisting. The high-load 57 mm Carbo has a broad working range. Use for main and jib sheets on centerboard and keelboats like Lightnings, Dragons, Solings, J/24s and for mainsheet systems on catamarans. Use for: Main/jib sheets Mainsheet fine-tune Control lines Vangs Cunninghams Outhauls