The perfect addition to the ruark audio r1 radio and the mr1 speakers the backpack 2 battery allows you to have 8 12 hours of wireless playback wherever you take it on a single charge the battery takes approximately 5 hours to fully charge it clips neatly to the back of the r1 and mr1 devices and use the 2 screws provided to secure the battery to the device playback time will vary depending on volume and screen brightness