This Aftermarket Push Button Switch has an integrated dust proof top and replaces Milwaukee 23-66-2665. This switch is mostly used in portable power tools; angle grinders, die grinders, etc.Switches are commonly replaced parts in power tools. A switch handles all on/off and variable speed functions. They also have a role in electric breaking; they can momentarily reverse electrical polarity. Because switches use mechanical internals, they tend to degrade and wear out over time, eventually requiring replacement.