Ideal SureTest Alligator clip adapter in black color is designed for real-time TRMS voltage|frequency and harmonics monitoring. It has an invertible display that helps to plug in upside down. Plug cab be used for 61-059 AFCI or GFCI circuit tester. It measures THD percentage and logs periods of 3 percent. Plug is a selectable thresholds based on the most accepted international standards that will default to ITIC.