Here we go. It is a threaded choke tube that goes into the muzzle. There should be one in the muzzle of each barrel. One should be full choke and one modified choke. The EAA's come with three choke tubes, IC, M, and F. The T bar is to get the tubes out if ya can't unscrew them with your fingers. You should not tight the choke with the T bar, just your fingers. I would take out the full choke and put in the IC for CAS.
Slim