HT331B Sensitivity: A25-cent coil 65mm. Iron pipe-tube in Φ20mm 120mm. Temperature environment: 10-50℃. Operating Frequency: 25 KHz Operating Current: < 8mA. Alert audio. Power: 6F22 9V×1. Size: 392mm (operation); 258mm (storage). Low power consumption and long working hours. Beep sound when metal detected. Fold-away design for easy storage. LED power indicator.