... coupling class T and SM, so do Ultra High Strength Sucker Rod Coupling, using 4142 steel barCOMPANY PROFILEYantai Yunsheng Petroleum ... founded in 1997, is a professional manufacturer of API 11B sucker rod couplings, including Spray Metal coupling, class T coupling, ... AFTER SPRAY WELDINGHRC 56-62, ≥ 480 HV0.2THREAD STANDARD ROLLER THREAD, 10 THDS/IN, API 11B STANDARD Spray Metal Sucker Rod Coupling