Canon CP-E4 is for use with 580EX-II, 580EX, 550EX, 540EZ, MR-14EX, MT-24EX Speedlites. Accepts eight AA-Size Lithium, Alkaline and Rechargeable Ni-MH or NiCd Batterries. This battery pack reduces full power recycling time from about six to 1.7 seconds and increases the number of full-power flashes per charge from approximately 100 to 432. Dust-resistant and water-resistant battery Canon CP-E4 pack