I overall like these very much. Im in the middle of slowly building up a custom DMR and these are useful for helping get that sort of look with you m16. That being said they can be a little hit or miss. I first ordered 2 one feeds flawlessly it is a perfect magazine. The second had some feeding trouble if I used semi auto, but only at a certain way through a full magazine. I figured it was a factory defect and I was correct. Disassembled it, fixed where the spring was catching in the track, and reassembled with no issues. Even though it was a tiny issue for what you're paying for these I'm surprised they don't test them more diligently for defects like this.
Light yet sturdy construction
Easy to disassemble and reassemble (both for repair and cleaning purposes)
They usually feed flawlessly (unless you win the defect lottery, lucky me)
They hold 70bbs which to some may be a con, but I prefer the lower capacity which really isn't that low
The one magazine can with a small defect. (Likely a rare circumstance snf it was easy to address)
Had to modify mag pouch for them (I measured a full size mag, cut a piece of Styrofoam to make up the difference and put it at the bottom of my mag pouches. It works flawlessly)
If you're thinking about getting these I would. After fixing my mag I liked them so much I ordered 3 more. Also I figure that something being defective is a slim chance coming from a company like magpul especially since they're charging you $20 per mag.