I carry a Park MT-1 "Dogbone" multitool on all of my bikes. It's light at 40 grams, small and inexpensive but durable. It has 3,4,5,6 and 8 mm hex keys, a small flat screwdriver and 8,9 and 10 mm box wrenches. The larger hex keys are oriented to have decent leverage. It and a Ritchey CT-5 chain tool , three tire levers and a CO2 inflator valve and cartridges have accomplished all of my road side fixes, mostly on other people's bikes.