Perko battery switches are designed for surface mounting. Standard duty switches have a bright red polycarbonate housing for safety with a large easy-to-turn black knob. The housing of the heavy duty switches are red fiber-reinforced polycarbonate. Selector switches are designed with a "make before break" feature. This allows switching between the "1", the "all" and the "2" positions while the engine is running. Models with an "Alternator Field Disconnect" feature offer protection for Non-Unitized Alternators should the switch accidentally be turned to the "OFF" position with the engine running.