Fully Machined from S7 shockproof tool steel with a tensile strength of 275,000 PSI; Optimized hook design for maximum strength and case rim contact; Hook location tolerances held to +/- .001"; Radiused corners for extended life and smooth feeding; Full diameter rear shaft holds tension longer over factory parts many times over; Heat treated to optimum hardness and cryogenically treated; Guaranteed for life against breakage or we will replace at no cost to you; Black Finish