For use in 2 or 3 Wire Circuits ACCURACY GUARANTEED Electromechanical meters only - FOR USE ON 120V SERVICE OR 240 V SERVICE Weatherproof - Industry standard | Plugs in to any 4-terminal meter socket | Rated 120/240 volts | Use on circuits up to 200 amps California Type Approval for Single Phase watthour meters (S-02S-CA20023, S-02S-CA20023E & S-02S-CA20023-LCD)) only Also available in 400 amp "K" Meter - no CT's required!