It's 21cm. I think I replaced the shoelaces with thicker ones because I couldn't tie a bow properly yet, but I don't think there are any particular problems with using them. I bought them new a year ago and used them twice a week for six months, so they show some signs of wear, but there is no noticeable damage to the opening or any noticeable scratches on the surface. - Brand: Umbro - Color: Blue - Material: Synthetic leather Thank you for looking.