When you have a variety of flat magazines the ST3 will do the job for you. Although not purely a flat magazine, the G2s / Slim Series have a light stagger that we have fitted inside this ST3 model and that last few rounds go in a lot easier with the simple 4 step process you need for make ST3 do it's magic. Ladies especially like how it maintains a nice set of finger nails. ST3                    16.5mm x 37.5mm • 5/8†x 1-1/2†Most Single-Stack Magazines