Goal zero rock out v2 rechargeable speaker amped up sound toned down size for excursions and impromptu dance parties the rock out 2 portable speaker amplifies tunes from your mp3 phone or laptop for over 20 hours without draining battery power from your device compatible with any device that uses an audio output jack easy controls on the outside of the speaker so you can safely store your device in the speaker and zip it away features recharge by usb solar run time 20 hours