I think a serious BOB needs more than just throwing the obvious like clothing, a knife, water, food, etc in a duffel bag. You have to prepare carefully your personal emergency contact information like addresses and numbers of area hospitals (as many as you can in your area), the police department number, the local poison control center number, emails of all your family members and contacts because sometimes emails can get through when calls cannot, etc. It takes some time and meticulousness, not only money investment. Your BOB is relative to your emergency plan and if it doesn't call for one, so be it. Don't put one together...