Ronstan's Series 30 Ball Bearing Utility Blocks are a range of lightweight blocks with high static and dynamic load capacities and versatile head fittings. They feature precision-moulded, UV-stabilised acetal sheaves running on acetal ball bearings to give high performance and low friction. The 2-stage ball bearing system provides consistent performance over the full load range. They are ideal for primary lead blocks on dinghies and catamarans and control lines on larger yachts.