In a word, cavernous. As an experiment I loaded up 10 pistol cases in the main compartment and there was still a bit of room left. Of course then the bag was heavier than that small planet I mentioned. Still Im rather happy that I have a range bag that can fit just about anything I would need at the range. Silly but I actually can fit my dedicated .22lr range bag inside and still have room for all of my things and tons of room left over. I do wonder how well constructed this bag proves to be. Its very easy to load it up and end up with a bag that weighs more than the stitching can withstand.