I already carry ca 7 pairs of gloves (I work in a lab so just grabbed a handful and shoved into my bag, all sized for me 7-8 though). I carry 5 4"x 4" nonadherent dressings (my FAK bag was specifically chosen to be at least the size of a 4x4 to allow carrying these - is 5 enough, should I automatically just fill any extra space with these as the most useful things I could carry?). I carry tape of different kinds (but probably not enough).

The tape and dressings can be improvised if I run out though as you pointed out. It was useful to find out what gets used most in an ambulance though as it does sort of indicate that I carry roughly the right things.

However what I was trying to get at was things that couldnt be improvised easily but could be invaluable to someone with training. The IV is a good suggestion of this type but although I would be willing to carry the giving set I seriously doubt I'd want to carry around enough solution to do any good (I doubt 100 ml of saline would be enough!). What are your thoughts on instruments, airways etc etc. What stuff that can't be improvised would be useful?