This electrical tester set includes a Clamp Meter (Cat. No. CL600) and a GFCI Receptacle Tester (Cat. No. RT210). Klein Tools CL600 Electrical Tester is an automatically ranging true mean squared (TRMS) digital clamp meter measures AC current via the clamp, and measures AC/DC voltage, resistance, continuity, and tests diodes via test-leads. Exclusively designed from the ground up by electricians for electricians. Years of field research, combined with extensive input from electricians across America, inspired the development of meters loaded with innovative, time-saving features. Klein Tools Receptacle Testers are designed to detect the most common wiring problems in standard and GFCI receptacles. A convenient chart on the tester helps determine wiring condition in outlet, based on LED lights results. Conditions indicated: open ground, reverse polarity, open hot, open neutral, hot/ground reversed.