Fits Winchester, Mossberg, Browning, H&R and other shotguns, that use the Win-Choke, Invector or Accu-Choke thread pattern. Pure Gold extended non-ported chokes are designed to optimize the Federal Flitecontrol Wad shells to give you the ultimate pattern that you have been looking for. They are not designed to increase maximum range, rather they are designed to provide more shot in the kill zone at reasonable ranges. All of our chokes are made from a top grade 17-4 heat treated stainless steel for maximum strength and durability. PLEASE SELECT .555 OR .570 IN THE COMMENTS SECTION.