This dual power source for exclusive use with the EOS-1, EOS-1N, EOS-1V and EOS-3 allows quick switching between the standard 2CR5 lithium battery or four AA-size alkaline-manganese or NiCD batteries, according to the shooting conditions. The camera operates even when only one of the two battery types is installed. Compact and lightweight, BP-E1 is an attractive alternate power supply grip that offers enhanced flexibility in power source selection.