Ronstan Core Block® are a true all round solution. A tuned 2-stage bearing system provides excellent performance across the full working load range with an integrated thrust bearing feature and the resilience to handle high dynamic or static loads. Acetal & aluminium sheave options, alloy cheeks and stainless fixings complete the durable package. For reliability and a long service life, these Ronstan blocks are the right choice for sheets, halyards and control line applications for cruising and racing.