The Nikon MB-D15 Battery Grip Pack for D7100 from Nikon is a battery grip designed for use specifically with the Nikon D7100 digital SLR camera, and accepts one EN-EL15 battery. With one battery in the MB-D15 and one in the D7100, your shooting time is effectively doubled. Moreover, when one battery is drained, it can be removed and recharged while you continue shooting with the other battery. In addition, the MB-D15 can utilize 6 AA batteries and comes with the MS-D14 AA Battery Holder that slides into the battery grip. It can also be powered by the optional EH-5b AC Adapter (with EP-5B Power Connector).