Those pre-packed kits are expensive, and we find that they dont' really have what we think we need--or at least what we use.

So here is what we use most---and carry in our FAK:

Multiple band-aids of various sizes
Advil, Tylenol, Imodium, Pepto-Bismol--4-10)tablets of each.
Some alcohol wipes
Neosporin/anti-bacterial ointment
A couple of rolls of pre-wrap flexible bandage
An Ace bandage (we've never used it)
A partial roll of white adhesive tape
A sewing kit--more for the tent than for us!
A knife
A few gauze bandages

I think that's about it. Our theory is that if we need serious first aid for a compound fracture, heart attack, or major burns, we are not going to be able to provide that anyway. We just focus on what we can fix/ameliorate...and go for help if we need more.

And we are careful to avoid needless risks.