MOBOTs are single-walled to be lightweight and maximize water volume. Fill it with cold water for an icy roll; MOBOT & Chill! Deep Tissue Massage and Hydration. Perfect for everyday use and high-performance activity. Stress relief at your fingertips! Big Bertha is the size that started it all. It's everything you need to stretch and roll out your entire body, plus drink two bottles per day and you've met your hydration needs. MOBOTs are lightweight, convenient and save you time and money. Designed to go with you, so you can feel good anywhere! We combined a sustainable water bottle and eco-friendly foam roller to help your body and the planet.