For use with systems under 50 volts. Capacity - 250 amps continuous, 360 intermittent. Surface Mount. Plastic housing. Improved design to protect the copper contacts and brass terminals used as electrical connections. Size": 5-1/4 dia. x 2-5/8 deep. The Alternator Field Disconnect (AFD) Model will prevent damage to the alternator if accidentally switched to the "OFF" position while the engine is running.