This one is purely for last resort and holds .45 long colt rounds or .410 shells. I prefer to have one chamber for warning, then the other for business. The cool thing with these derringers is that the barrels are interchangeable, so you can have different caliber possibilities. I'm going to get a 357 magnum barrel for this gun as well.
Plus, I have that XD-9 which holds up to 16 rounds per clip. I have two clips for it and it is concealed as well.