I bought one of the off the shelf kits about 5X9X2"
And actually needed it one day and realized how inadiquite most kits are. they are set up for minor cuts and bruises.
I used my kit to at best patch me up till I could get the the drug store and get better supplies.
Since them I have added to the kit.
I added needle add thread, Dental lits, bigger bandages, Ace bandages, Different bandages, creams, and Pills (cold Medicines, clearatin, Imodium, Advil, asprin, and a few others.
I then went to Wally World and bought a Tackel box that has the plastic boxes.
Then walked over to the pharmacy section and put together a first aid kit.
The top section has gauze ace bandages, and other large blood soaking or clotting products.