Hi just to throw another in the loop, I have used the Brownell line of mags for about two years and have not had a failure. They have just the magazine or a tactical one that already has a better spring, follower, and mag pul on the bottom. The price works it self out about right and your ready to go right out of the box.

They are made here in the U.S. and Brownells is a reliable company to do buisness with. They are very military and law enforcement friendly and donate to a lot of military and police memorial charities. Plus they have one price shipping, so no matter how much you order its still one set price. I usually put in a large order once a year to get the most bang for my buck so to speak.

Here are a few links for maintance of your magazines

http://www.brownells.com/.aspx/lid=10351/GunTechdetail/Brownells-AR-15-M-16-Magazine-Maintenance

Replacing the spring and follower

http://www.brownells.com/.aspx/lid=10362...wer-Replacement

And on the magazines themselves

http://www.brownells.com/.aspx/lid=13221/GunTechdetail/Brownells_AR_15_M16_Magazine_Test

good luck.