Lewmar'S Synchro Blocks Are Engineered For Speed, Efficiency And Superior Handling. We Use A Combination Of Scientifically Optimised Block Geometry, A Free-Spin Bearing And Self-Aligning Head To Reduce Friction And Increase Efficiency By Up To 40% Over Budget Blocks On Mainsheet Systems. Each Component Is Perfectly Synchronised With The Movement Of The Rope, Providing You With An Easier, Smoother Transfer Of Power From Deck To Sail And Less Wear On Your Rope.