The Vivitar Battery Grip provides the power you need for the Nikon D3100 SLR digital camera. It adds to the power by using 2 EN-EL14 rechargeable, high-capacity batteries. In addition, the battery pack provides a vertical shutter release, that makes holding the camera in the vertical orientation as easy and secure as in the horizontal position.The versatility of using the Battery Grip is three fold. Two EN-EL14 rechargeable batteries will allow you many hours of uninterrupted shooting. Plus the vertical shutter release will make vertical shooting as comfortable as the horizontal format.