1) Meets ISO9001:2000 and TLC standard (http://tlc.cttl.com.cn/english.php) 2) SC, FC, ST, LC, MU, E2000 type optional 3) Ceramic and phosphor bronze sleeve tube optional 4) 100% test before shipment 5) Accurate external size 6) Excellent changeability and directivity 7) Hybrid and duplex type optional Welcome to inquire!