Carbo AirBlocks® are 60% stronger and 30% lighter than our classic blocks. Use the 40 mm Carbo for jib and mainsheet systems on high-performance dinghies and for loaded control lines on small keelboats. The nylon-resin sideplates are densely packed with long-glass fibers for a compact block with a high strength-to-weight ratio. Sheaves spin on high-load ball bearings with fitted races for low-friction operation. Ball bearings, sheave and sideplates UV stabilized with black additive for maximum protection. Use for Main/jib sheets, Mainsheet fine-tune, Control lines, Vangs, Cunninghams, & Outhauls.