The ABC (Akuna Brass Catcher) is a picatinny/weaver rail mounted brass catcher. The craftsman who makes them will customize it to fit your pistol, so it can potentially be used on any pistol with an underbarrel rail. Rather than just having bag held to the side of the pistol, like its competitors, the ABC has a rigid frame with netting that sits above and to the side of the pistol. It looks far more reliable than the cheap brass catchers I have encountered, but the customization does not come cheap. At $79.95 it costs twice as much as other rail mounted brass catchers.