It's 18.5cm. My child outgrew them after about 3 months of use. I generally washed them weekly in the coin laundry shoe washing machine. They show signs of use, so I've listed them as having scratches and dirt, but they're still in good condition. I think they can still be used. Please refer to the photos for the condition. Therefore, I'm selling them at a low price. Please purchase only if you understand and accept this.