- Minor issues out of the box.
The short version for those who don't like to read: These magazines may require some minor hand fitting (and this is something that can happen with real-steel firearm magazines in some cases).
If you are willing to work with that, then I recommend these magazines. If you want instant gratification out of the box, you might be better off with a different mag. The Echo 1 600 round hi-cap that came with the gun did not have any fitting problems.
These magazines were very difficult to lock into place on my Echo 1 Red Star AKM AEG because the metal on the front edge of the magazine was just slightly too wide.
This problem can be easily resolved by very lightly filing away a small amount of metal from the sides of the front edge of the magazine with a hand file. Don't use a Dremel or any other powered grinding tool because you can take off too much metal too quickly.
If you try inserting and removing the magazines several times, the black finish will rub away, making it very clear exactly where the metal on metal contact is occurring.
Otherwise, these are excellent magazines. Don't try loading them with a standard magazine loader tube; the BB's will fly back in your face once you try to fill the mag beyond about 70 rounds.
The UTG magazine loader (the one that is shaped like a pistol mag) works very well for loading these magazines.