The manuf.s like Dorman and AC Delco don't provide a new 'O' ring in the package when you order a new Vacuum actuator switch. Does this mean none is required? Does it mean you should reuse the old dirty, wonky O ring that has been on the original switch since the truck was put into service. Or does it mean they are trying to 'cheap out' and cut costs? I fear it is the latter. There is a groove in the base of the switch below the threads for an O ring to fit. Don't reuse the old ring which has been distorted and nicked and may not seal properly. Thanks for letting me say that. Jim