I just installed one on my 870 20 gauge and got it sighted in two weeks ago. I then made my own comb riser out of an old neoprene scuba wetsuit. Used it for the first time this weekend hunting squirrels. I wasn't used to aiming without my cheek firmly planted down on the stock and missed my first one, but figured out how to trust it and started hammering them. Small learning curve, but I think it will work out for me just fine.
FullChoke