40mm Dynamic Single Stand Up Block.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.Stand Up - This block is assembled around a lacing eye and uses a spring to hold it upright. Ideal for spinnaker halyard blocks which are deck mounted or any other control line where the block needs to stand up. Becket - The 40mm range features a large central hole, which can be used as a becket (tying-off point).