Bought several of these at the local Cabelas - not a bad price.

BLACKHAWK!® AR-15 30-Round Magazine : Cabela's

Built of heavy-duty stainless steel
Anti-tilt follower for reliable function
High-quality spring provides even pressure

Made of heavy-duty stainless steel with an anti-tilt follower for reliable function. High-quality spring provides even and consistent pressure for confident cycling. Removable bottom plate for convenient access, easy cleaning and maintenance. Made in USA.