Made to hold a 32 Rounds Colt Sub Gun Mag, will also hold a Glock 33 Rounds mag. Pouch is made tight tolerance, stiffness, and a pressure foam to secure mag. You can hold pouch upside-down with a fully loaded mag and it will be retained by the pouch. (You will have to shake pouch upside-down hard for mag to pop out). Yet they still draw out easy for a quick reload.