Series 30 blocks offer smooth running performance with low friction. Used as primary lead blocks on dinghies and catamarans, they are also suitable for many control line applications on larger boats. Impact modified, fiber reinforced and UV stabilized 1-3/16" Zytel sheaves Acetal ball bearings and sheaves 316 stainless steel load straps and head fittings High load versions feature a Nylatron sheave suitable for both rope and wire