I carry a multi tool, CO2 inflator, 2-3 CO2 cartridges, 1-spare tube, some tire levers, a Schrader to Presta valve adapter and a patch kit. I got a flat before my commute yesterday morning, I replaced the tube with a new one, but brought the old tube to work, located the puncture and patched it. I then had a spare tube for the ride home and hopefully longer.