Helps diagnose wiring problems on trailers and tow vehicles. Bright LED indicators provide clear and easy-to-read test results. Quickly and easily identifies wiring and connection problems. Checks tail, brake, turn signal, and reverse lights. Compact and easy-to-use design. Ideal for automotive, RV, marine, and utility trailers. Plug-and-play operation with no complicated setup. Compatible with 4-Way flat trailer socket connectors ⚠ WARNING: This product can expose you to Lead, DBP,CD, BPA ,hexavalent chromium, which is known to the State of California to cause cancer. For more information go to www.P65Warnings.ca.gov.