... casings and couplings 2. Multi-tooth thread, 8API Round 3. Twin-lock 4.Good qualit and Good Price As a professional and ... in multi-tooth and single-tooth, round and buttress threads, 3,4,5,8,10 TPI available for cutting J55, L80 ... welcome to contact us by phone and e-mail. Twin-lock Multi-tooth Carbide API Inserts for couplings