Completely sealed breakaway switches to automatically set trailer
brakes in case of accidental trailer breakaway. Required by law in some
states. Emergency use only, not to be used to lock brakes when parked or
stored. 2010 and 2005 have reinforced nylon case, weldable metal tab,
nylon pin assembly and are rust and corrosion free. 2009 has all metal
parts and a brass pin assembly