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 a self-lubricating Nylatron® sheave suitable for rope and wire, and stainless steel 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.