A stun grenade includes a cartridge having an explosive charge in communication with a fuse and a housing including a closed end, an open end, a longitudinal axis and including an internal cavity which accommodates the cartridge. An end cap is attachable to the open end of the housing, the end cap including an end wall and a side wall. A plurality of spaced first vents are defined in the end wall of the end cap. A plurality of spaced second vents is defined in an end wall of the housing. The output from an explosive charge is optimized by vents having a straight flow path. The vents have a first end in fluid communication with the cavity and a second end in fluid communication with an exterior periphery of the housing.