Trulock Choke Tube EXTENDED WITH BLACK FINISH RETAY 20 GA FEDERAL TSS # 9 SPECIAL F9RTY20 For the absolute tightest patterns, use TrulockŪ Federal Heavyweight TSS choke combined with the FederalŪ Heavyweight TSS shotshell. The TrulockŪ FederalŪ Heavyweight TSS choke is made from high strength, heat treated 17/4 stainless steel with a black oxide finish. This choke has been optimized using hundreds of rounds of Federal Heavyweight TSS shell to give nominally 400 pellets in a 10 inch circle at 40 yards.