I carry a 3, 4, 5mm allen wrench. I carry two spare tubes, no patch kit. I carry 1 co2 cartridge with chuck but I also have a Lezyne Mini pump strapped to one of the bottle cages bolts. I normally just pump a flat with the Lezyne has no trouble getting to 95-100 psi which is what I ride although it will take about 200 strokes but not difficult. I would use the CO2 in a hurry or on a ride with someone but I am soloist 99% of the time. CO2 is ok but it can sometimes get out before you get things all in order and I require an endless supply of air to be cautious. They fit in a small saddle bag. If a chain breaks I use my cell phone and I have broken a spoke too. I have not broken a chain yet but that can happen. In some cases you must make the dreaded call for help.