1、Feature: This adapter is a lighting and cable tester for trailers and towing vehicles, which has fastest and easiest search for cable line defects on trailers and on towing vehicles. 2、Easy Operation: Defective cable colors are indicated by the device via LEDs. All 7 pin sockets and plugs can be checked, press the test button and a fast diagnosis is made. 3、Application: This trailer adapter features a unique plug and play design that eliminates the need for cutting or splicing. Applicable for trailers caravans horseboxes bicycle carriers. 4、Battery Powered: The battery tester is battery powered (not included), no external power source is necessary. Use on towing vehicles with a control unit for trailer operation is not possible! 5、Tester Material: Made of ABS plastic, which has good insulation and best durability, the contact material is copper, which ensures better connection.