A muzzle brake or recoil compensator is a device connected to, or a feature integral to the construction of, the muzzle or barrel of a firearm or cannon that is intended to redirect a portion of propellant gases to counter recoil and unwanted muzzle rise.
Best frame there is at the pricepoint. It fits all tm-spec just fine, and the only difference compared to an advanced GSB frame is that the housing unit is just a little bit more wobbly