A cracking little watertight first aid kit, the Ultralight/Watertight .3 fitted neatly into just about every activity we took it on almost invisibly. Being incredibly tiddly - 12x10cm by 2.5cm thick - it slid neatly into bikepacking framebag pockets or even hydration packs as a permanent fixture - until needed of course.
Being so small it only really contains minor injury materials: plasters, antiseptic wipes, a sting relief wipe, assorted plasters and small bandages, but it also sports a few items for more meaty injuries such as safety pics for making a sling, a length of fabric tape and a few butterfly closures for larger cuts.
Of course this kit may not save your life, but it could certainly make finishing your day off a little more comfortable after some cuts and bruises - and it only weighs 60g so it can be forgiven for that. This is the smallest kit Adventure Medical Kits offer, so if you are after something a bit more capable, just check out their website - they are all very practical and well specified off-the-shelf kits. We did notice that our pack wasn't as well specified as the one on their website and was missing some tweezers and pain killers, but there has possibly been a specification change as the packaging on ours reflected exactly what was inside.
Experience suggested we throw in a few painkillers and a tick removing tool to boost the usefulness and the waterproof fabric bag was big enough to swallow that and more, with the waterproof zip easily reclosing over the lot. It was all very neat and easily stowed.
If you are taking part in an event where first aid kits are specified, this would likely fill the obligation without weighing your race pack down, but don't expect too much - that little case isn't a Tardis after all.