60mm Quint Dynamic Block With Becket.Designed for use as a low friction mainsheet system on sports catamarans, but suitable for many other applications including backstay tensioning on keelboats.For a complete 11:1 or 12:1 mainsheet system, you will need:A2169 - Pro-Ratchet 60mm Quint Block. A2040 - 40mm Dynamic Single Block.Bearings Ð Dynamic Blocks feature our patented bearing system which uses twin rows of stainless-steel ball bearings running on a stainless-steel rail. This provides a superior load-carrying ability and longevity when compared to other bearing systems available on the market.Swivel Lock Ð The A2069B comes with a removable swivel lock moulding. When installed, the shackle can be locked in 90-degree orientations. When removed, the attachment shackle can spin freely.Becket Ð This pulley features a central becket between the sheaves. The becket can be removed by undoing the split ring. This allows for easy termination of a spliced rope or the addition of another block to increase the purchase system.