The Through-Deck Dinghy Block is compact and lightweight, with fast trim and release under high or low loads. It is designed for dinghies and control lines on larger boats. Do not use the Through-Deck Dinghy Block on heavy course racing keelboats, scows, or catamarans. Free-rolling Delrin® ball bearings, sheave and sideplates UV-stabilized for maximum protection. The block is reinforced with high-strength stainless-steel straps. Used for Sheets, Control lines, Traveler controls, & Cunninghams