I have bought 4 of these mags so as to be able to use my SRC AKS-74U for more than a display piece and have noticed a recurring problem. Primarily the magazines have a design flaw in the fact that they lack reinforcements on the front lip, where you "Rock" the magazine into place. This flaw means the mags are susceptible to breaking when jarred in the weapon. While this is highly irritating, as long as you are gentle with the mags, they can still be used in a combat environment. Seeing as how the SRC AKS-74U uses proprietary magazines, if you want to use that weapon in a fight these mags are a must have.
30-45 rd capacity (Almost identical to real steel mags)
You get 3-4 mags on one gas fill
Works fairly well in colder temps (35+/-)
Very weak front lip
Requires a gas mag speed-loader adapter to be loaded (King arms works just fine)
Super stiff mag spring