The lightweight alternative to a block, with no moving parts these are an extremely low maintainance item. These rings are hard anodized with PTFE coating to provide the smoothest wear resistant surface possible.  The Windesign low friction rings are available in 2 sizes and can be used in various applications. Make your own 4:1 mainsheet block-ring combination The 38mm ring is mainly intended to create a 4:1 mainsheet system. Similar to the existing Optiparts block combination, the EX1319, you can replace the 29mm Harken block by the 38mm Windesign ring. By changing this block, you create a low friction, less heavy and more durable block combination. It's easy to create the block combination as shown below yourself. What you need to make the 4:1 mainsheet block-ring combination: EX1314 - Harken 40mm block on Vectran line with a safety snap shackle EX1322 - Windesign 38mm low friction ring EX13672 - A bit of 2.2mm Vectran line