The OOFOS story begins with the OOriginal Sandal. This combination of sleek design and revolutionary OOfoam recovery technology lays the groundwork for all future styles and models. Revolutionary OOfoam technology absorbs 37% more impact than traditional footwear foam materials to reduce the stress on your feet and joints. OOfoam technology absorbs 37% more impact than traditional footwear. Patented footbed design reduces stress on knees, ankles and other joints. Closed-cell foam is machine washable and designed to minimize odor. Feel the OO PromiseTry any pair for 30 days risk free. If you're not 100% satisfied, you can send them back at no cost.