I picked up some new magazines this week, some of which are Thermold Master Molder. I got some 20 and 30 rounders for .223, as well as this one for a 7.62x39 AK. The ones for the AR were all very nice looking, good fit and finish, fit well, feed well, etc.

This one for the AK though (I only got one, so I am unaware of the frequency of this problem) had some major issues with grinding on the magazine port. You can see I inserted it once, and it took some materiel off. This is concerning since I was not especially rough with it, and the plastic just scraped right off, in a semi thick layer.
Note: This grinding was happening on both sides.

I circled the blemish with a pencil then inserted again.

You can see where the grinding is still happening.

I decided to take my Dremel to it, with a small grinding pad. I took a thick layer off the rectangular section outlined below.Here you can see my hack job. Again I was surprised at how soft the plastic was. I am not at all trusting of the durability of this product, and will only use it for the range if at all.

I had to take equal(ish) amounts off from both sides.

It now seats appropriately, but after grinding right below the feed lips that much I would imagine its integrity is compromised to some degree. $6 for range mags might sound appealing, but it may turn out to be more of a liability if it ever finds its way into your "serious business" gear, and causes problems right when you are counting on dependability.