Portable Pocket PA Voice Amplifier Booster Speaker Megaphone for Teachers Coaches Tour Guides Promotion Sales Very loud, clear and low feedback, extremely suitable for teachers,tour guides, coaches, promotion use, etc. Portable waistband voice amplifier with super mini size (4.1*3.3*1.4 Inches). Long durable time when fully charged (about 15 hours). Can be used as an MP3 speaker for Iphone, Ipad, audio player, etc., connected by audio cable(male to male). Firm for its ABS plastic material.