An IFAK (Individual First Aid Kit) is sized and stocked to treat one person, typically the wearer or a single casualty, and is built to be carried on a belt, vest, or bag. A mass casualty kit is built for multiple patients at once, with redundant tourniquets, dressings, and chest seals bundled together for a school, workplace, or vehicle to respond to an incident involving several injured people. The two aren't interchangeable: an IFAK runs out fast in a multi-casualty event, and a mass casualty kit is too bulky for one person to carry as personal gear.

Match the kit's location to where you spend time and where an emergency is actually likely to happen, not just where it's convenient to store one. A home kit covers the place most people spend the most hours, but it's no help if something happens while you're out. A vehicle kit matters because a meaningful amount of trauma, yours or someone else's, happens on or near the road, and it travels wherever you drive. An EDC bag keeps a kit with you anywhere you go on foot, and a duty belt or vest keeps one on a law enforcement officer specifically because their job carries a real, direct exposure to trauma. The kit that actually helps is the one within reach when something happens, not the one that's technically owned but left behind.

A pre-stocked kit has already been tested to fit its bag's compartments and pocket layout, so you're not guessing whether everything will actually fit once it's assembled. Building your own means matching components to the bag's actual internal dimensions, not just picking good gear, since an item that's slightly too bulky or the wrong shape can throw off how the whole kit organizes. It's still worth doing if you want to customize contents around your own training and local regulations, or need specific items a pre-stocked kit doesn't include, just budget time to test-fit everything beforehand.

A public access bleeding control kit is meant to be mounted in a fixed location, like a school hallway or workplace, where anyone nearby, not just one trained person, can grab it during an emergency. It typically focuses narrowly on stopping severe bleeding: a tourniquet, gauze, and a pressure dressing, kept simple enough for a bystander with little or no training to use under guidance. An IFAK is personal gear, carried by one person and often stocked with a broader range of supplies for that person's specific role or training level.

A resupply kit replaces the components that get used up or expire in an existing kit, like tourniquets, gauze, and dressings, without paying for a new bag or carrier. It makes sense once you've actually used items from a kit, or when sterile components approach their expiration date and need rotating out. Buying a resupply kit is usually cheaper than replacing the entire kit, since the bag, pouches, and any reusable tools don't need to be repurchased.