made by high quality alloy steel with advanced heat treatment,and all size of sucker rod available in grade C,D,KD, ... Use Office Monogram Issued by American Petroleum Intitute and acquired ISO9001 Cetificate of Registration and became the firstfirm of passing "Dual Registration ... API in China. product gradeC,D,KD,H, L,HY and Polished roddiameter(mm) 5/8"3/4 "7/8 "1 ...