Sizes 3, 4, 5, 6, 7 are considered infant and run small. Size up 1-2 sizes. The soles are a foam like/rubber material and lightweight for new walkers. These sizes do zip. Sizes 7, 8, 9, 10, 11, 12, 13, are toddler sizes and run big. Size down 1 size or stick to normal size if you want room to grow. These are hard soles. Sizes 1 & 2 are youth sizes and run big. Size down 1 size or stick to normal size if you want room to grow. These are hard soles. The inside where the leg is placed is genuine soft leather.These are handmade in so there wil