PU Leather Material: The surface made with waterproof PU leather and shoes bottom is soft rubber, inner is warm plush inner. Rubber Sole Design: The boot used rubber material, it's anti-slip and soft for protection and safety.Baby can feel comfortable and warm in the winter. Velcro Design: The boot side with the adjustable velcro, you can adjust elastic and easy to wear on or off. Boot Inner: Cozy fleece lining perfect for those cold winter days. Suitable for newborns, infants, babies, toddlers and little kids' winter. Size Reference: Inner Length: 12.5cm(4.9inch)=Fit for 6-12 months, 13.5cm(5.3inch)=Fit for 12-18 months, 14.5cm(5.7inch)=Fit for 18-24 months. You had better measures your baby feet.