You have to be very careful when you buy Thompson mags. Some of them look like they've been drug thru a mud hole, stomped on and had a fast coat of paint put on them before they put em' up for sale. I got some from CDNN that were like that. I had to order from Northridge for "new" Thompson mags and they were $30 bucks each. M3 mags may be easier to find since the gun was in service longer and now that the ban is over Uzi mags in 45ACP will start showing up again. Just watch out for "used" Thompson mags because most of em' are just that, "USED" big time.