The right fist includes accelerometer technology that can detect different movements and responds with sound effects. Kids can move the right fist up and down for certain action sound effects or repeatedly smash a surface to increase the sound of Hulk’s roar. Requires 2xAA batteries, included. Punch the air or hit a hard surface to activate sounds and Smash like Hulk!. With 3 ways to activate and exciting Hulk sound effects, the Hulk Smash FX Fists let kids imagine gearing up like their favourite gamma-green hero!. For children 5 years and over.