Bought one for my Polymer80 build. As expected with all SLR products, fit and finish are perfect. It fits like a glove and really helps push you hand high up on the gun. IMO, the flare is perfect. Its enough to help get those mags quickly in but not obnoxiously large like some other companies.
My only gripe is that while it fits the Polymer80, it doesnt work with 10rd mags when used in that gun. Fortunately, the OEM base plates are made of plastic and a few minutes with some sandpaper, you are able to sand down the edges and the mags will lock in no problem.