I modified 1 to try in a Colt mag.
I ground it down to the same length in the rear as a factory follower about 5/8in. and the front to slightly longer than factory length about 1/4 in. with a slight taper on the lower corners so you can roll it in under the floorplate retainer (the little spring steel part that goes in the slot on the floorplate on a straight 20) and get it lined up on the ribs of the mag.
It works and is a PIA to get in there.
INMO after all done in a straight 20 you are just as well off with alloy followers or green ones in a straight 20rd. mag.
I found the rear to be critical if long it will bottom out early and not let 20 rds in or make it hard to seat mag in gun when full, not allowing smooth feeding as the rds are jammed tight between follower/floorplate and bolt. So 1/2in. on the rear leg of the follower will giv that little extra clearance needed.YMMV.