Features: brand new and high quality Our tester pen is made of high-quality plastic materials, practical and durable. Self-check before use, please hold the pen tip with one hand and for touch the tail with the other hand.When the light is on, it means the tester pen is normal and has sufficient power. As long as it is close to the insulation of the wire, the plastic for shell of the electrical appliance, etc., When the light is on, it means that the line is live. One hand touches the bottom of pen, and the tip of pen touches the wire. The breakpoint is where the light goes out.Easy to trace hot wires. This is a flexible tool that provides a unique ability to check holiday lights and power to ensure they are capable of being lit and used. Specifications: Material: Plastic Pen Tip Length: approx 17mm/0.67 inches Total Length: approx 138mm/5.43 inches Handle Width: approx 14mm/0.55 inches Power: 3xLR41 Button Battery Package Includes: 1x Tester Pen note: 1.Please allow 1-3cm errors due to manual measurement, make sure that you do not mind before you order. 2.Due to the difference between different monitors, the picture may not reflect the actual color of the item.