Shoe size table:Size 21 inner length 13.3cmSize 22 inner length 13.8cmSize 23, internal length 14.2cmSize24 inner length 14.7cmSize 25 inner length 15.2cmSize 26 inner length 16cmSize27 inner length 16.8cm Size 28 inner length 17.3CM size 29, inner length 17.8cm size 30 inner length 18.3CM size 31 inner length 18.8cmSize32 in length 19.3CMSize33 inner length 19.8cmSize 34, internal length 20.3CMSize 35 inner length 20.8CMAttention: Please choose the size based on the child's foot length+1cm. Thank you This model is an induction light with a large battery and a large capacity. It uses the battery inside the car's remote control key and is made of two large batteries. The most important thing is that it is waterproof and can withstand water ingress without causing any problems. It can usually light up for several weeks or even months