1. The nap zapper is an anti-drowsy alarm 2. Worn behind the right ear 3. Works on the principle electronic balance. As the driver's head nods below a preset angle it emits a loud alarm signal alerting the driver to take corrective action, take a break or even take a nap. 4. The nap zapper is perfect for people who need to be on full alert while on duty such as security guards, machine operators and even students who need to work on their posture. 5. Blister Packaging: L: 124mm W: 92mm