I have a zip-type from Western Belt. I consider it a good way to increase what you have with you every day without bulking out your pockets. I also like to think it has a chance of staying with me if I get mugged.

The space available in this type is very small. I have some paper clips, a short ferro rod, striker and tinder. It is not really accessible in a hurry. There isn't room for, eg, a photon freedom, or a 1 litre plastic bag. I also carry money in it, and it's surprising how much space that takes up, especially if you use small, spendable denominations. $100 bills may not be the best form of cash in an emergency.

Apparently stuff in cheaper belts can "print through" the material to leave a visible outline. I've not had that problem, perhaps because my belt has a plastic strip inside the pocket.