类型 : 1. One is male and female, i.e. one end is male thread and the other end is female thread, which we call sb, (OK, this is just a code) 2. One is double-way, i.e. both ends are internal thread or internal thread are through, which we call SN.
类型:1. One is male and female, i.e. one end is male thread and the other end is female thread, which we call sb, (OK, this is just a code) 2. One is double-way, i.e. both ends are internal thread or internal thread are through, which we call SN.