Luckily Midway has a good return policy. When I tried the new mag in my 6906, loaded or unloaded, the slide would not close, nor would the gun chamber a round. The mag wouldn't eject if it was inserted with slide closed. I didn't measure it but it appears the mag is a trifle too long. The new mag had no markings on it and seemed to be made of a rougher looking unpolished steel.
I called Midway to advise them that maybe that shipment of backordered mags was out of specs. She said their supplier was sure they were S&W factory mags. I don't think so.

Dave