40mm Dynamic Single Block with Removable Ultra-Strap.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.Removable Ultra-Strap Ð Our patented Ultra-Strap is used in our 20, 30 & 40mm Dynamic blocks. The Ultra-Strap is unique when compared to other designs because of its coining process. This process strengthens the strap, making it more reliable and hard-wearing as well as making it rope friendly. The Ultra-Strap block is a great choice for dinghy jib or mainsheet systems.The strap is held in place with a bolt and nut. It can be easily removed to allow quick and easy fitting. Becket - The 40mm range features a large central hole, which can be used as a becket (tying-off point).