This block is great for lightweight vang systems. A.677 Cam Cleat – This block features an allenite cam cleat with over fairlead. Click here for cleat details. Swivel Head – A built-in swivel pin allows this block to swivel once attached. ideal for applications where the pulling forces may change direction. The swivel cannot be locked. Bearings – 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 which run on a plastic rail. Fiddle - The fiddle is a secondary smaller sheave which can be used to create an inline purchase system for a smaller lower loaded application. The fiddle features ball bearings. Becket - This block also features a removable clevis pin, for easy attachment or release of a spliced rope. It also allows this block to create a 4:1 purchase system.