4 x Energizer CR123A CR123 123 3v Lithium Photo Battery
Also Known As 123, 123A, CR123, CR123A, DL123A, VL123A, CR123R, BR2/3A, CR17335, CR17345, EL123AP, K123LA, L123A, PL123. CR123 is the most common size, and is also widely used in security alarm systems.