Currently, HTC makes the holster for two gun families: most Glocks, and the Sig Sauer P226, P229, P220, P227, P228, and M11-A1. Off the rack, the holsters are sized for the longest gun in each family, so if you use a compact model, like a Glock 26, there will be empty space in the bottom of the holster. The way they’re molded, it makes no practical difference, but if you like, you can order a cut-down version of the holster if you only plan to use smaller guns. On the plus side, if you have both a full size and compact in the same family, like a Glock 17 and Glock 19 or 26, then the same holster works for all. If you’re a Sig user, you might see a little bit of shake because Sig uses slightly different slide widths across the P22X family.