The Bluetune-Pop portable Bluetooth speaker from Divoom features an integrated Class-D amplifier with four watts of power and a built-in rechargeable lithium long life battery for up to eight hours of music. Connects via Buetooth or USB cable. The speaker's Pop-in/Pop-out mechanics allow the sound system to be reduced to a pocket-size of about three inches when popped-in using its spring mechanism. When opened, the additional housing improves the sound quality and volume for clear, full sound. Just $40. See it at www.divoomusa.com