Harken’s Grand-Prix mainsheet systems are critically important options for high-performance beachcats like the Nacra 17 or F18s. The high-efficiency blocks making up these systems feature insert-molded ceramic bearings that almost eliminate rolling resistance, greatly improving power transfer to the crew for easy, precise trimming. These compact blocks feature hardcoat-anodized sideplates that envelop composite sheaves for easy disassembly/reassembly. The system profile is the lowest on the market by far. High-performance fairing increases aerodynamic flow and protects the crew and blocks from impact damage. The lower block features a built-in cam arm that infinitely adjusts by loosening two (2) screws with a hex key. A single ratchet sheave in the bottom block ensures release is controlled and smooth. A snap shackle attaches the block to the boom. A swivel shackle attaches to the traveler. Note: the GP mainsheet system is delivered as a 12:1 mainsheet system, but can be easily reconfigured as a 10:1 or an 11:1 to align with wind or crew preference. All necessary parts and reeving instructions are included. Line not included.