Fit information from the manufacturer:
Double-stack fits wide-body mags for Glock, including Glock 36, Para Ordnance, STI, Browning, Beretta, Sig, FN Five-seveN, etc.
Easy-on, easy-off, but totally secure and tough as nails. The same as the AUG/AR pouch, but smaller for a pistol-caliber magazine. Friction fit with no straps. Can be ordered in a left- or right-facing horizontal version (see guide below). Fits up to 1?" width belts. SOF/IPSC legal.
Fast access due to the strapless friction fit, quick-detachability and good concealability make these single pouches especially suitable for varying conditions when you may want to carry more or fewer magazines.
Break in instructions from the manufacturer:
BREAK-IN PERIOD FOR MAG POUCH FITTING
Our mag pouches are polymer lined and use friction to maintain a snug fit on magazines. This polymer liner takes about a week to mold to your mags and may seem really tight on the insertion at first. We advise leaving the mags in at night. When inserting mags into the pouches, roll the mag in front to back, using the index finger along the magazine's spine and the round noses of the bullets to open the pouch mouth a bit as you push the mag in.
Once broken in, magazines are easily inserted, held snugly, and release like smooth, greased lightning on the withdrawal because of the nylon skin of the pouch. Our pouches do not bind like Kydex, which often forces you to pull perfectly straight up to get the mag out. They are also more consistent than many leather mag pouches whose tension seems to vary a lot.