SafeHigh-quality:Our tester pen is composed of a high-quality and durable PVC Handle, screw rod, slotted point screwdriver, nut, spring, neon bulb tube, and resistance block, which ensure safety while using. Self Check Function:In self-check before use, please hold the pen tip with one hand and touch the tail with the other hand. When the light is on, it means the tester pen is normal and has sufficient power. No light indicates that the battery needs to be replaced. Automatically Induction:As long as it is close to the insulation of the wire, the plastic shell of the electrical appliance, etc., when the light is on, it means that the line is live. The brighter the light, the higher the voltage of the tested circuit, and vice versa. Find Line Breakpoints:One hand touches the bottom of the pen, and the tip of the pen touches the wire. The breakpoint is where the light goes out. It is used to find breakpoints in daily household appliances such as rice cookers, computers, and plug-in boards,etc. DC Detection:Please touch the bottom of the pan with one hand, touch the positive terminal of the battery with the tip of the pen, and touch the negative terminal of the battery with the other hand. When the light is on, the battery is fully charged, and vice versa. SPECIFICATIONS color: as show Size: 0.314cm/0.15.5" Input Voltage Range: 70-250V Package includes:2Responsive Electrical Tester Pen