Things I liked: Solid and heavy, replicates real loaded M4 mag. Will shoot two loadings of BB's on one charge=76 rounds per charge. Easy to fill with BB's with KWA aluminum tube loader (holds 30 BB's) or KWA magazine style high volume loader. Pyramyd had the best price I could find on these magazines. The weight of the mags replicates a fully loaded 30 round M4 magazine.
Things I would have changed: I have three KWA magazines and two of the three came from the factory with loose fill valves. I would advise you get a tool and check yours before charging. Also, several screws were not snugged. They take small metric allen wrenches, .5mm and 1.5mm. These magazines are expensive compared to AEG type magazines, but they are well made and durable.
What others should know: I put Magpul's original magazine pulls on these magazines. The center pull tab offers drop protection, and doesn't interfere with charging the magazine with gas. I would recommend these magazines to a friend, and will buy more for sure.