This is a Birkenstock insole. The size is 24.5. It has only been tried on once indoors. It is recommended to use it two sizes smaller than regular sandals. BIRKENSTOCK The blue footbed is an insole designed to mimic barefoot walking. This insole is modeled after the footprints of healthy feet left in the sand. It firmly supports the natural movement that your feet seek. The heel part, which wraps around the center of the heel, promises stable walking. It also firmly supports the arch of the foot. For those who want to experience the comfort of Birkenstock in shoes from other manufacturers. Please try this blue footbed. Footbed designed with the shape of the foot in mind Firmly holds the heel, providing excellent stability Thoroughly absorbs shock Ideal for flat business, leisure, and sports shoes