I bought quite a few 5.45X39 blackened stainless steel magazines from CProducts years ago when I got my M&P 15 in that caliber. Those magazines were flawless. Shiny? Yeah, but they functioned 100%.
So, a few months later I bought 20 of their aluminum 5.56X45/.223 magazines. Six of the twenty would not feed the last two rounds out of the magazine. Got several promises to help with that here when I mentioned it in other magazine problem threads. However, no one would respond to the e-mails sent to the address they gave in the threads here.
I haven't bought a CProducts magazine since.
For the last 10 years or so I buy PMags or GI aluminum magazines from DSG or PSA. Never any issues with those.
As they say, your mileage may vary. This is just my experience and it's several years old.