Sub sucker rod coupling: 1) Material: Seamless Alloy Steel 40Cr (AISI 5140) 2) Standard: API Spec 11B 3) Type: Full Size and Slim Hole 4) Grade: T, SM 5) Other Size: 5/8"*3/4"; 7/8"* 1"; 1"* 1-1/8" 6) Characters: It is used to connect different sizes of Sucker Rod or to connect the Polish Rod to Sucker Rod string. Wooden case, international seaworthy package.