Our Baby Slipper are made with pure wool. Dyed and crocheted by hand with a extra soft sheepskin lining and tough leather soles for long lasting comfort. These slippers have the elasticity to stay put without being overly constrictive on young growing feet. Newborn: Recomended for 0-6 months B3: Recomended for 3-14 moths B5: Recomended for 1-2 years The sizes reflect hard shoe sizes. A B3 would facilitate a hard shoe size 3, a B5 a hard shoes size 5. They go up every other shoe size. If you are already wearing a 4, buy a 5.