Features: A profeional tester for identifying the polarity of magnetic field fastly and safely. Pen type magnetic tester, mini and portable. One button operation, easy to use. The north and south polarity can be distinguished by the two signal lamps(red = N pole, green = S pole). Comes with a sturdy plastic tool case. It can be used for the determination and identification of permanent and electromagnet poles, magnetization polarity check, and coil test. Specifications: Material: ABS Sensitivity: 5mT (50Gs) Display: 2 LED lights (red = N pole, green = S pole) Service Temperature: -20~80 Storage Temperature: -40~150 Power Supply: 2 * 1.5V AAA battery (NOT included) Item Size: 154 * 27 * 24mm / 6.06 * 1.06 * 0.94in Item Weight: 64g / 2.27oz Package Weight: 263g / 9.30oz Package Size: 22 * 10.5 * 5.7cm / 8.66 * 4.13 * 2.24in Packing List: 1 * Tester 1 * Storage Case 1 * Manual (English) Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.