Product Description: Used? 40mm (4 Ω x 2W) full frequency internal magnetic horn with strong bass and strong penetration; High pitched, pure and beautiful, transparent and delicate; Can you bring it to all? Connect audio devices with a 3.5mm audio interface (such as iPhone, MP3, MP4, laptop, etc.) to play music; Three AAA batteries can be used for power supply; Can be connected to a 5V DC power supply for long-term use;