I picked up 10 of these, the last time there was a deal, And I wouldn't recommend them either.
The build quality of the magazine body is great, the plastic body is stiff, seems very durable and has no flex or give. Here's the problem. As the person above me mentioned, these magazines simply will not feed properly when full to capacity (30) rounds. They work great when they're loaded to 26 or less rounds, but that's beside the point. I payed good money for something that doesn't work as advertised.
Stick to aluminum GI mags, PMAGS or something that will work with 30 rounds loaded.