Kleinn Air Horns Sealed 40-Amp 5-Post SPDT Relay is expertly engineered to keep high amperage away from pressure switches to extend their life. Relays have hundreds of uses so it is worth it to keep several on hand. This Kleinn Air Horns Sealed 40-Amp 5-Post SPDT Relay is a sealed unit with 5-post connections and features Single Pole Double Throw (SPDT) technology. It is manufactured for durability with an attractive Black ABS housing.