Fiddle with cam for min 6 and max 10 mm ropes, sheave Ø 50 mm, max working load 450 kg. Lewmar Synchro blocks are simple, reliable, engineered for reduced friction, lightweight and resistance. There plain bearing locks are typically used for heavy and static loads in: halyard tuning, mainsheet systems, mast foot blocks, mast head blocks and boom vang. The composite sheave slides on a synthetic Free-Spin bearing while stainless steel reinforced cheeks prevent ropes for wedging. Practical switch from swivel to fixed shackle. All models are compatible with Lewmar bases and eyebolts.