These magazines are made of light and VERY durable plastic. These mags can take abuse. I've dropped them, sat on them (were in my dump pouch), kicked them.....basically put them through hell. With basic care every now and then, I've never had a jam, misfeed, problems with these magazines...although I only load them about halfway. Each magazine can hold a maximum of 105rds, which gives you a total of 1050 bbs to sling.....plenty enough for anyone to effectively give support fire. At less than 8 dollars each (depending on where you buy them from) these magazines are perfect for the player on a budget.
One downside is that the mag comes quite shiny, but plenty of use will dull the finish.
Another thing I like about the mags is how easy they are to disassemble and clean.
Twist the circle either left or right, it will pop off once it's in a horizontal position from the spring pressure.....so be carefull because they can fly if your not paying attention.
Now the spring will come quite fast, and if your not paying attention....it can send the 'spike' in the spring flying out. The 'spike' is there so when you put on the circular cap, the spring doesn't get caught up or binded (which would happen to me when I used to own a m4 and m14).
And here's the entire mag disassembled.
Overall I would give this product a 9.5/10 for the lack of finish. However, since they're plastic I don't think they could look any better.