The Sigma PG-21 Power Grip is a specially designed battery pack with a vertical grip and vertical shutter release that is dedicated for use with the Sigma SD14 Digital Camera. It can hold two BP-21 batteries simultaneously - thereby doubling the effective shooting time of the camera. Power Source): Li-ion Battery BP-21 (two or one); Dimensions: 141mm(W) x 109mm(H) x 72.5mm(D); Weight: 300g (without battery).