Recoil inserts are the quick & easy way to repair damaged threads or creating stronger original threads in alloys & composite materials in original equipment manufacture. Made from corrosion resistant stainless steel, they create stronger threads in most materials & simplifiy changeover from unified to metric or vice versa. They reduce thread wear & are interchangeable with other brands of inserts or tooling. Size. 3/8 UNC X 16 TPI Length. 1 1/2 x Diameter.