"This tester has one side to connect a trailer's 7-pin plug and another side to connect a car's 7-pin plug. This tester quickly indicates whether a fault is in the car's wiring or that of the trailer Features: Can effectively test what is the problem compatible 7 pin plug and socket connection Carefully selected materials, frosted surface Cross slotted copper needles, cooperate with the female pin Size cross is more easy to control.(The slot size is not stable) Safe and reliable percompatiblemance, reasonable design, skillful appearance, convenient operation Features: Main material: ABS+Copper Color: black Battery: 9V (not included) Size of Item: 190 * 40 * 40mm / 7.5 * 1.6 * 1.6in Item Weight: 150g / 5.3ounce Package Size: 200 * 55 * 45mm / 7.9 * 2.2 * 1.8in Package Weight: 194g Listing Package: 1 * 7 Pin" Trailer Test Tool