These are CO2 powered sound-flash Hakkotsu Thunder B grenades. The grenade is CO2 powered and sets off a loud >130 decible BOOM when they detonate. The core is re-usable but each use expends one shell and one 12g CO2 cartridge. These are very loud and give the user a definite tactical on the field and especially in CQB environments. This package includes three shells and one core. The core is 100% compatible with all brands of Thunder B replacement shells. The Shocker core differs from the standard core in that it has a larger (2mm) hole on the end cap that allows the CO2 to vent faster, making the grenade explode nearly instantly. The tripwire can be set across paths or in doorways to eliminate unsuspecting enemy team members!