I keep it in this tupperware box, which is about 12"x9" - pretty decent size. It's not packed to the gills. First up was going through the checklist that lives with the kit itself.
Sadly, because I'm a loser, this checklist is left over from the last time I went through the kit, and is no longer accurate. So I just checked again and made additional notes.
Missing this time: two rolls of vetwrap, the lube, the 60cc syringe, the scissors from the suture kit (huh?), the tube of banamine, one of the two pens, one of the two bags of electrolytes.
The antibiotic ointment had expired, as had the saline solution. I threw away the antibiotic ointment but saline solution doesn't really expire, thanks marketing guys.
I tested the flashlight batteries and the in in the pen, then the thermometer - I stuck it into my armpit. I once nailed some Pony Clubbers on their horse management inspection because while they had a digital thermometer, the batteries were dead. Since then, I've been very careful about checking my own during these inspections, because: karma.
Some things I decided not to replace: the second pen, the second roll of tape, the scissors, and the second dose of electrolytes.
Some things I replaced right away: I had already replaced the banamine and just kept it in my main tack trunk, so I transferred that over to the kit. I have enough leftover vet wrap to cover my entire horse head to tail, so it was easy to grab two rolls out and get them to the kit.
I stopped by Walmart on the way home and bought more lube (which necessitated a fair bit of considering time in front of the personal pleasure section at Walmart while wearing my breeches, earning me more than a few sideways looks), a tube of antibiotic ointment, and one addition to the kit: a travel size tube of antibacterial hand wash.
I am not a big believer in the stuff on a daily basis, but I've seen how effective it can be around the barn for biosecurity. Every new horse gets a quarantine stall and a big pump jug of the stuff on the door. Our barn is an interesting confluence of several circumstances - rural area with a few other not-great barns nearby, super-fancy and $$$ horses in for training or sales all the time, one or two pregnant mares or new babies at all times, and a very particular ban manager. It's really great, but it does mean there's a higher level of care taken about that sort of thing.
Today, I stopped by Tractor Supply and picked up another 60cc syringe with catheter tip. Pre-surgery, I had a half dozen of these around; during Tristan's rehab, one after another succumbed to broken parts, staining from betadine, or just plain old got lost. Time to re-up.
All I have left to do is update the inventory list and the emergency contact information inside (new barn, need to add the fiance since he would probably care if something terrible happened).
Always bring peppermints!