This category lists all Camera Battery Grips available from Outdoorphoto.  A battery grip allows you to run the camera on two batteries at once which lengthens the working time available before you need to change batteries, often allowing you to complete an entire day's shoot on one charge.  Another advantage is that you can more comfortably shoot with the camera in portrait orientation as the DSLR battery grip provides a duplication of all controls (shutter button, exposure control dials and exposure lock functions).