This part is to make your 20 gauge 1100 / 1187 cycle properly with target loads. I've drilled out gas ports on some, but this does the trick without modifying your barrel. I'd never shoot magnum shells anyway... but there are always those who would take a high grade gun hunting.

Here is the reply Remignton's tech support: "The barrel seal activator should only be used with low brass shells. The "rule of thumb" is basically to use it only when the gun will not cycle. Thanks," I likely bought the last five of these in existence. Willing to part with one or two.