The BP-40D/50D is a Premium Series Vertical Grip/Battery Holder for Canon EOS 20D,30D,40D, and 50D cameras. This battery grip can hold two BP-511A or 6 AA size batteries to offer double-length shooting time. It is also equipped with a vertical-grip shutter button, control dial, AE lock/FE lock button, and AF point selection button to make shooting with the camera in a vertical position just as comfortable as shooting horizontally. The battery grip comes with a holder for 6 AA batteries and a holder for 2 BP-511A batteries.