40mm Dynamic Single Swivel Hook Block with Fiddle and 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 Hook Head Ð Featuring a 360-degree swivelling hook for super easy attachment. Ideal for lightweight control systems where removal needs to be quick.Fiddle - The fiddle sheave is a 20mm dynamic bearing sheave. This ensures that any purchase systems run as smoothly as possible.Cam Cleat - The A..77, small aluminium cam cleat, is mounted to an adjustable stainless steel arm. The arm can be adjusted to suit your sheeting angle by simply loosening the nut and bolt through the centre of the block, loosening the side plates and retightening everything at the required angle.