I've got a bunch of different ones, but my surplus steel mags are my go-to mags. The Chinese ones are my favorite.
I'm not sold on the sealed floorplate of the US Palm mags, especially after seeing pics posted online of floorplates that came undone- and US Palm's immediate threats to the guy posting the pics. They also claimed to have a steel "cage" molded inside the top of the mag within the polymer feedlips, and it turned out to be more of a steel bracelet that didn't go into the feedlips. The guy posting about that was shushed also and his pics were taken down. Seemed like a bad coverup of a mediocre design. Their mags may work fine but for 3 times the cost of a 100% proven steel mag, I'll pass.
Check out the bottom of this page, Arsenal does drop tests with some of the more popular polymer mags: K-Var Corp. ™
I have a bunch of steel 20 round mags that came from somewhere in East Europe. I can't remember which country and probably couldn't spell it anyway.
It think I got them from Aim Surplus, and mag pouches were included.
They are pretty handy shooting prone or off of a bench.
The circle 10's are a good mag, but for me it's hard to justify the cost when the relativly cheap steel mags work so well and last for decades.
I have just a few circle 10's only because I need them (with U.S. made floorplates) to be 922r compliant with a couple of guns.
I wish I had a lot more of them.