Beautifully made tubes with an extremely smooth inside finish and an undercut, tube-to-barrel joint to minimize shot and wad fouling buildup. Both Win-Choke and Tru-Choke tubes are "invisible" style, no unsightly "knob" sticks out. And, they can't rust; they are stainless steel. Install/remove with a quarter. WARNING: FOR USE WITH LEAD SHOT ONLY. Mfg: Colonial Arms SPECS: Approximately 1-1/2" (3.8cm) long. Stainless steel. Threads are as follows Tru-Choke-style Thinwall are .774"-44.