My long ride saddle bag holds:

2x inner tubes
Topeak Mini 20 Pro multitool
3x 12g CO2 cartridges + Innovations Air Chuck SL
Park glueless patch kit
Park emergency tire boot
Sram Powerlink (if chain breaks, remove offending piece and replace with link)
Schrader valve adapter (as a last resort to fill up tires at a gas station or with a generic pump)
House key (as in a single key, not the whole damn keychain)
2x latex gloves + chemwipe

All fits quite nicely in a small Topeak Wedge. I'm confident that will get me home through any mechanical short of a catastrophic wheel failure which would probably send me to the hospital.