What back up gear do you take?

[tracydr]

Among my list of 'spares' I bring:

extra mask
extra complete reg set (inc computer/SPG)
spare 'loose' SPG with HP hose
mouthpieces
zip ties/zip tie 'gun'
complete BCD inflator assembly ready to just screw into the wing (inc spare inflator LP hose, corrugated hose, power inflator)
spare OPV (for BCD wing)
2 spare weight pocket inserts
mask defog (several bottles)
spare assorted batteries/travel power strip/charger
small tool set (adjustable wrenches/needle nose pliers, allen wrenches, picks, Leatherman folding multitool)
spare assorted O-rings/lube
small digital scale
(3) SMBs
signal mirror
whistle
Nautilus Lifeline
Jotron strobe
(3) lights
(3) pairs dive socks
(2) beenies
gloves
blunt tip knife
titanium line cutting tool
aligator clips (for hanging wet things)
bungies for securing tanks

.........just a few things that immediately spring to mind.......there's more where that came from.......

This looks very similar to mine. When I use my old fins with straps, I would bring a spare fin strap,too.not sure about the small digital scale, although I have a tiny fish scale which would be handy to check bag weight before packing.
my husband and I take one of most things between the two of us as spares, plus a save-a-dive,save-a camera toolkit and extra flashlight batteries.
Learned my about spares when I broke a fin strap on a trip to Africa and nobody else had a spare strap that would work on my fin. ( I now have spring straps). I almost had a completely ruined trip over a fin strap. Thankfully, one of the DM's had a spare set of extra small fins.
I like to wear my spare computer somewhere on my kit, so that I won't miss a beat if a computer dies.