Sleep in comfort all year round with Outlast® technology. Outlast® is a ‘phase change’ material, which means it actively responds to the temperature outside. When you’re too warm it absorbs heat to cool you down. If you get cold it releases heat to warm you up. Now you can have uninterrupted sleep, which is a must if you want to feel happy and fulfilled with the Thermocool Outlast Mattress Protector.