Features: A professional 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 celsius Storage Temperature: -40~150 celsius 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)