Found this while looking for marlin parts, http://www.gunpartscorp.com/ad/1163640.htm#1163650

Those are actually pretty good mags, I bought a few, else where, and use them for bench shooting, yet to have a jam.

I love my Canuck thermolds....  that is a good price

I bought a bunch for $5 ea a few years strictly  to shoot 5.45 in and thought I did alright. They're good mags.

I have 6. They work well with a wide variety of ammo but don't always lock the bolt back and I've had the BCG outrun the mag spring a couple times.

They're definitely worth $3, that's close to what I paid.

They work fine unless your running a suppressor Only way I ever got mine to jam...

I have 5 that I bought from Centerfire Systems back in 2010.  I bought several at the time because they were the only 20 rounders available.  They have all run fine, although I can't say I've abused them.  I had two that were loaded for at least 4 years and the feed lips did not loosen, all of them hold rounds.  The only issue I've had with them is that the bolt hold open didn't work on all of the mags.  The ones I kept all hold the bolt open.

I bought 35 from Numrich and 6 do not consistently hold my bolt open.  They other 29 did.  All of them drop free and the samples I tested all hold rounds, including dropping from chest height on the floor.  That's as far as I tested the new ones, I have not shot them yet.

The first batch that I bought and the new batch that I just received were both Wilson NC, LEO only mags from the 90s.  There are several generations of Thermold 20s and I feel that the Wilson NC, LEO marked mags are the best shot at getting a good one.

Yeah i ordered six, cause I like the shorter 20rd design for varmint hunting but I dont like using my colt mags seeing as how these were so much cheaper than a magpul its like why not.

Ill have to see when mine were made when they get in.

So whats the difference between the AR15 mags and the M16 M4 mags?

One is for "machine guns " and MUST be more dangerous.. .should ban  them probably
Kidding. .  .no idea why they listed them that way.

I'm pretty sure that Numrich has some kind of not-so-great inventory tagging system that creates multiple listings.  I had the same thing when I was buying Makarov mags from them and the same mags would show up in multiple listings for different gun "types".

I bought "M16" mags, because, you know, I'm pretty high-speed.

Thanks, I just picked up 4 - for this price, why not.

Just purchased 5 to try out. I'm starting to enjoy 20rd mags more than the typical 30. Never heard of Thermold until this thread

I found Thermolds at a local pawn shop. Ive read mixed reviews about them from this site over the years but the ones I saw were made in NC instead of Canada and at $5 each I got at least one to test out.

EDIT - My Thermold didn't even make it to the range. It didn't drop free from any of my ARs or my friend and roommate's AR, and as I was loading it, a round popped out. Upon closer inspection, I saw a crack which I did not notice before and the feedlips were bowing out. I purposely butt-smashed the mag which caused the crack to get even worse to the point of the mag splitting in half. Good thing it was only $5, total junk.

Good thing, i ordered ten of them.

Me too.  I have 2 from somewhere else that are fine for my needs.  I hope these next ten are just as good...  Thanks for the tip, Gbirner.