External Flash Battery Pack CP-E4 Replacement with Protective Carrying Case and Screw Mount Professional Flash Battery Pack Replaces Canon CP-E4 /8x AA This Professional External Flash Battery Pack is an external power source for a higher flash capacity. 100% BRAND NEW!! 1 Year Warranty! The Pack uses 8 AA-size batteries (same batteries as flash) prior to a shoot to ensure fast and smooth transitions from one battery set to the next - important in critical shooting situations or to keep up momentum in the studio. Ideal for the professional.