... for its good quality ,especially for is self-locking/anti-loosening thread technology This product was based on US ... patent 4,171,012, 4074950 and US Military standard Mil-N-85353. Initially, this technology ... 80s. Gradually, it is used widely in auto and many other mechanic industries in US, then around the ... this product fully met US Standard. Self-Locking and Anti-Loosening Thread Tap ...