A decent nylon mag pouch - DeSantis Nylon Single Magazine Pouch

This is one sturdy and not so expensive single mag pouch. I actually use it to carry stuff other than magazine - leatherman multitools, small flashlights.

However, I found that the Glock 20 10mm double-stack barely fits, while the XDM 45 double-stack fullsize is also a tight fit. The cover can barely reach the velco. However, it's an excellent pouch for other double-stacker, maybe a bit thick for single-stack. It's also an excellent fit (feels like it's designed for it) for the 9-round compact XDM 45 mag.
Pros: Sturdy, option to mount vertical/horizontal
Cons: Fits 9mm/.40S&W, not so much for double-stack .45/10mm

This review was written in the old system and had content requirements that are different than reviews written today.