Perko Heavy Duty Battery Selector Switch w/Alternator Field Disconnect [8603DP]Diameter: 5 1 4" Depth: 2 5 8" Polycarbonate Body with Brass Terminals Ignition Protected For use with 6 to 32 Volt Marine Electrical Systems Capacity 250 AMPS Continuous, 360 AMPS 5 Mins. Intermittent Terminal Stud Size: 5 16" When used with Non Unitized Alternators, these models will interrupt the field current (reducing the possibility of damage) if turned "OFF" with the engine running. Specifications: AFD: Yes Lockable: No Positions: 2 Continuous