the big advantage a ploychoke has over screw in choke tubes is that the choke can be changed with the turn of a wrist. while polychokes are ugly to say the least , they offer a shotgunner up to nine different chokes with little effort. polychoke now come with a screw in system for tapped shotgun barrels that accept individual screw in choke tubes. they are available from brownells for $99.95 and once screwed in to the barrel they offer nine different settings.a fixed polychoke is a rather permanent attachment when brazed on to the end of regular untapped shotgun barrel. they also have vents or ports in the tube, before the shot pattern reaches the choke constriction,thereby reducing recoil. pbl