Recently ordered four of these magazines after experiencing good performance in a variety of AR-15 type platforms with prior purchases. These units are definitely well-used and often are coated in fine, talcum powder-like sand. I disassemble them and wash them thoroughly before re-assembly.
At any rate, three of the magazines I received were quite serviceable with one appearing virtually new. The fourth magazine's lips were so worn that the follower was not adequately retained after the last round fed and had to be carefully extracted from the receiver.
Spoke with Apex customer service to relate my experience and the representative expressed her concern and is sending me a replacement magazine sight unseen. I truly appreciate Apex empowering their CSRs allowing them to respond positively to their customer's needs.