Honestly, I'd rather have a FAK than a PSK if I had to pick ONE (1), singular, to bring with me and a decent knife. The little one that lives with my PSK (same size tin) is just the basics, but there isn't a lot you can pack into a tin that is less than 4" square and just over a half inch thick.
The pic is a little dated, I've added 2 large eyed needles (NOT for stitching- taped to the lid, they take up no space), 2 large X-acto blades (also taped to the lid, and also NOT for people), 4 Benydril and 6 Advil to:
-pair of nitrile gloves
-8 2x2 gauze pads
-6 3x1 adhesive bandages
-2 finger tip adhesive bandages
-2 butterfly closures
-water bag
-12 PA tabs, repacked (I had the space, redundancy is a good thing

)
-spectra fishline (tiny, no bulk, why not?)
-red electrcians tape, ~4 feet, works better than surgical tape IMHO
-ear plugs (I always seem to need them after I've used a first aid kit, and not to drown out the screams of the maimed as has been proposed)
-12 tylenol
-12 asprin
-20 immodium (2 full courses)
-6 tums
-2 ranger bands
-~3' of electricans tape, wrapped around the sides
In my bigger kits, I've got bigger medical modules. My ditch kit has:
2 pr nitrile gloves
1 trauma dressing (the older military type)
1 cravate
1 2" roller gauze
4 4x4 gauze
14 bandaids
2 knuckle bandaids (in pouch)
2 fingertip bandaids (in pouch)
6 closure strips
1 small roll of duct tape (I bet everyone saw that coming)
3 provo-iodine wipes
4 alcohol wipes
12 asprin
12 tylenol
6 advil
20 immodium
6 benydryl
8 sudafed (the real thing)
1 pr tweezers
1 surgical prep razor, 2 razor blades
8 medium safety pins
1 pr earplugs
mini Bic (it fit here, not a bad place to have it)
inventory sheet
My BOB has a nearly identical kit, but it has two trauma dressings, more gauze pads (2x2 and 4x4), more meds (quantity and variety), two 4" rollers rather than a 2", spare purell and a think of liquid bandage, at the cost of the spare lighter, tweezers and razors but I carry a SAK in my BOB. And since if I'm wearing BOB on my back my ditch kit is on my chest...
Yeah, I'm set up for some bumps and bruises if the stuff hits the fan.
