Optimize rig tension in any conditions, anytime to improve sailing efficiency. This easy-to-use, snag-proof system is designed for high performance sailboats, small keel boats and trailer boats. The black, UV-resistant acetal upper handle, fluted for a solid grip, installs on the swage terminal with six grub screws (included). The lower handle, in 316 stainless, fits onto the coupling nut of the turnbuckle with a self-locking collar for easy adjustment and repositioning. The system snaps down and locks away when not in use. Compatible with all Ronstan 5/16" threaded Sealoc turnbuckles in systems with 4mm, 5mm, 5/32" or 3/16" wire.