I have about decided to pick up a new M&P15 to keep the PTR-91 company. Looking at mags, and C-Products seems to be a good name on this forum. I found some new blackened stainless 30-round mags at CDNN on sale for $9.99 each, or aluminum for $7.99 each. Which is the best route to go, and am I correct in assuming that these C-Products mags will function and hold up well? Thanks.