40mm Dynamic Single Swivel Block with Ball Bearing Cam Cleat.New for 2023.Made from high-strength, lightweight glass-loaded nylon and featuring AllenÕs dynamic bearing technology for a high-performance block suitable for keelboats and dinghies.40mm dynamic blocks are perfect for use on main, jib and spinnaker sheets on dinghies and keelboat control lines.Bearings Ð Dynamic blocks feature our patented bearing system which uses twin rows of stainless-steel ball bearings running on a stainless-steel rail. The ball bearings are caged for further friction reduction. These features provide a superior load-carrying ability and longevity when compared to other bearing systems.Swivel Head Ð Featuring a 360-degree swivel head with a 4mm shackle. The shackle is load rated higher than the block, so although it might look small, it's plenty strong enough!Cam Cleat - The A..77, small aluminium cam cleat, is mounted to an adjustable stainless steel arm. The arm can be easily adjusted by loosening the central nut and bolt. The side plates need to be popped out slightly before the arm can be moved. Once set to the desired position, push the side plates back and then tighten the nut and bolt.