Wireless MIC for Teacher 1.Features:hand free ... ,USB jack 2.Certificate:ISO9001:2000 3.Lightweight:30g mic 4.laser,page up/down Wireless ... Microphone for Teachers,USB Wireless Microphone,Bluetooth Wireless Microphone Feature:1.Portable,convinient ... Battery Environmental protection.9. It can work for 30 hours,standby time :60 days.More ...