I don't know if it will work or not yet, because my roo isn't big enough for one, so I haven't ordered one. (well, not big enough for the one he'll wear when he's full grown, they have bantam sizes) I've read the reviews, lots of positive ones from people who bought the right size, followed the directions, etc.; negative reviews from people who didn't use it correctly/didn't follow directions strictly or didn't check on their birds often enough in the first couple of days. I figured I'd give it a try before giving up on having a rooster, since i can only have a quiet boy. He is turning out very handsome!
The thing is, out of four 'pullets' and two 50/50s, we got FOUR roos (and only one of the 50/50s was a guy). We can only keep one. So, we will find homes for the two friendly RIRs, a hungry somebody for the mean boy, and were keeping the EE roo. And even keeping ONE boy might be stretching the rules... I don't know if he's allowed. But nobody suspects a chicken wearing a dress and a crow collar to be a boy, do they?