The party prank alarm siren is 3" long x 2.5" wide x 1.75" tall. It requires a 9v battery (not included). It is made of wood, plastic and electronic circuits. It is equipped with a battery holder with a snap action lid, off/on switch and flashing LED light. The LED lights to indicate the on position of the switch and attracts attention of the people near it. The unit has a plunger switch that is turned off when the unit is placed on a hard flat surface. When the unit is picked up, the plunger switch turns on and the alarm siren screams. The alarm siren is very loud and ear piercing. The alarm can be silenced by placing the unit back on a flat surface or turning the unit off with the off/on switch. Have fun and enjoy!!!!!!!!!!!!!