Do not know for certain regarding the 40 cal, but the three mags I had that were represented to me to be ProMags in 9mm were absolute garbage. I could not in good conscience sell them; one I gave away, the other two I threw in the trash which is where such things belong. Purchased them from junk peddler on Gunbroker. I would recommend not even inserting such poor qulaity items into a fine pistol like a Walther P99, just makes no sense to me. Workmanship on the ones I purchased were poor and the company evidently does not even put their name on the product, at least the ones I had. At least Meg Gar puts their name on their mags, so if you have a problem, you know who made them. The base plate on the 9mm is larger than the factory mag and does look different, whether or not it looks bad is probably subjective decision, but it is defintely obviously different from the factory mag baseplate. I highly recommend staying with factory mags, even if there were problems with some of the 40 cal baseplates, still far safer to deal with S&W/Wather and Meg Gar than some company that will not even put their name on their product. My thoughts, I am only one person, maybe others had opposite experience they can share with you.