Meeting all ISAF (International Sailing Federation) requirements for strength, design and features for sailboat racing, these safety tethers incorporate a lightweight aluminum double-action safety hook, built-in stress indicator and welded O-ring for improved security offshore, whether racing or cruising. The stress indicator features a bright overload flag that is exposed when the tether is stressed to the point of needing replacement (about 900lb. of force triggers the flag). The boat-end aluminum safety hook has an easy-to-use double-action gate that automatically locks closed, so it won't accidentally release from attachment points. Yet, it's extremely easy to open in one ergonomic movement without pinching your hands. Internal elastic retracts when not under load, staying out of the way. Nonmagnetic, stainless-steel snap shackle at chest releases from the harness under load. High quality product completely made in Italy.