20mm Triple Dynamic Block With Inverted Cleat. Triple blocks are generally used in systems such as cunninghams or vangs, to give a larger purchase system. A.677 Cam Cleat - This block features an inverted allenite cam cleat with pro-lead. Ideal for ending a purchase system and holding the rope. Click here for cleat details.  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 which run on a plastic rail.  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 much more rope friendly than other designs. The Ultra-Strap was the first marine industry block designed to work specifically with a rope attachment.