50mm Triple Dynamic Block With Hook.The A2054HK is a high performing ball bearing block, designed to eliminate friction and allow rope to run at great speeds. This block was designed so it can be easily attached or removed. Ideal for catamaran mainsheet systems or tensioning systems. Bearings Ð Dynamic Blocks feature our patented bearing system which uses twin rows of stainless-steel ball bearings running on a stainless-steel rail. This provides a superior load-carrying ability and longevity when compared to other bearing systems available on the market.Swivel Hook - A large swivel hook allows for easy attachment. The hook can swivel 360 degrees. Becket Ð A large central hole not only reduces the overall weight of the block but also offers a rope friendly attachment, perfect as a tie-off point when being used in a cascade system.