20mm Single Multi Function BlockThe multi function block has a slightly different strap compared to the A2020. The A2021 multi function block is the base block used in the following variations: A2021F, A2021HK, A2021SC and all double and triple variations. The multi function head is designed to attach our swivel, fork and cheek adaptors to. It is also used for riveting to the double and triple ultra-straps. 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.Becket Ð Our 20 & 30mm blocks offer a large central rivet which not only reduces the overall weight but also offers a rope friendly attachment, perfect as a tie-off point when being used in a cascade system.