Bought 6 of the sig p320 mags, They did not fit into the magwell on either a sig p320 or a cmmg banshee, They were very tight and 2 of them actually stuck in the firearm. I contacted Promag. They sent a return tag for warranty and said that they would personally test the replacements. A month later the replacements came. They were loaded with oil and light grease. Same problem. I tried to get in touch with their tech department ( which is horrible to do, even by email). I was fed up and called Scheels They sent a return tag and refunded the cost immediately. Scheels is a great company ! I am done with Promag for good ! We checked the Promag sig p320 mags against a real sig mag and the promag is much wider ( over .030) which explains the problem.