Have not measured the chokes but the M/F chokes on the 28" barrels of my two barrel set 28 ga are very effective on ducks over decoys Big ducks is mostly what we have, mallards, sprig, etc. and I still have a supply of #6 and #5 bismuth loads. When that is gone I will load nice shot. I like that even better than Bismuth in other gauges I have loaded primarily 16 and 12.