Equip your compatible Speedlite with the external CP-E4N Compact Battery Pack, for faster flash refresh rates, when combined with the Speedlites internal battery, and extended shooting times with more flashes per charge (requires 8 x AA batteries). It is also water and dust resistant in order to ensure improved performance on outdoor shoots. Purchase an additional CPM-E4 Battery Magazine for faster battery changes. Compatibility Speedlite 600EX II-RT Speedlite EL-1 Speedlite MR-14EX Speedlite MT-26EX-RT