This is a Birkenstock insole. The size is 24.5. It is a new, unopened, and unused item. It is recommended to use it about two sizes smaller than your usual sandal size. 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 crave. The heel cup, which wraps around the center of the heel, ensures stable walking. It also firmly supports the arch of the foot. For those who want to experience the comfort of Birkenstock in other brands of shoes, please try this blue footbed. Footbed designed with the shape of the foot in mind Excellent stability with a firm hold on the heel Thorough shock absorption Ideal for flat business, leisure, and sports shoes