Obviously load it up with whatever you need. I took those photos with all kinds of different ammo just to show the versatility. My current trays from bottom to top are:
#3: All NATO 5.56mm including XM193, M855, and some tracer M196.
#2: All 7.62x39mm TulAmmo 122gr. FMJ.
#1: Mixed .45 Auto 230gr. FMJ, .45 Auto 230gr. JHP, .38 SP+P 125gr. JHP, and yes, 12GA Aguila Mini's, Federal 1oz. Rifled Slugs, and Federal 00 Buck for my Maverick 88 Cruiser.