This is an excellent betwetting alarm system, worked a treat with my son who slept so deeply he didn't realise he was peeing. Within 2 weeks he was completely dry at night! This listing includes the alarm device, 2 x batteries, mini screwdriver, instructions, and I am throwing in a waterproof sheet that you can put under the bottom just in case of any leaks, so this includes everything you need to get started with finally having dry nights. All you do is put the device on the arm and clip the sensor to nightware. The alarm sounds the second any moisture is felt in the sensor, immediately waking up the individual and alerting them to go to the loo. Also has a gentle vibration. Comes from a smoke-free, pet free home.