51-918, Incorporated heavy duty silver plated contacts. One piece die-cast housing sealed with O-rings at base and mounting stem to keep out dust and moisture. Two 3/4" and two No 10-32 copper alloy stud terminals hex nuts and lock washer. Continuous Rating (Make Break), Large Studs -180 Amps, Small Studs - 20 Amps, Intermittent Rating (Carrying), Large Studs - 1000 Amps (20 sec. "On" - 5 Minutes "Off"). Same as 51-918P.