Miller Automatic Twist-Lock Steel Carabiner with 1-Inch Gate Opening, 400 lb. Capacity (17D-1) EASY TO USE: Spring-loaded keeper allows carabiner to quickly engage and disengage; gate opening is 1-inch (25 mm) wide for easy access SECURE: Double-locking mechanism with twist locks at both ends of the safety carabiner for safe and secure attachment SAFE FOR HEAVY WEIGHTS: Proof tested to 3,600 lbs. (16kN); min. tensile strength 5,000 lbs. (22.2kN); Max. working load 400 lbs. (181kg); meets OSHA 1926.502, ANSI Z359-2007 and CSA Z259.12 requirements DURABLE: Carabiner is made of forged alloy steel and is plated with zinc dichromate to resist rust and corrosion and ensure long life span WARNING: Carabiner must be closed and locked prior to use. Inspect before each use. Improper use could result in serious injury or death.