Inner length: Size 21 - 13.3cm, Size 22 - 13.8cm, Size 23 - 14.2cm, Size 24 - 14.7cm, Size 25 - 15.2cm, Size 26 - 16cm, Size 27 - 16.8cm, Size 28 - 17.3cm, Size 29 - 17.8cm, Size 30 - 18.2cm This light-up shoe features a sensor light with a large battery capacity and long lighting time Because these are light-up shoes and do not use a USB interface, the battery in the sole is responsible for the lighting. Over time, this can sometimes cause one shoe to stop lighting up, or one shoe to be brighter and the other dimmer, which is normal. If there are lighting issues such as uneven brightness on the left and right, one light will turn on while the other won't, or color unevenness, we do not consider these issues as quality problems. If you mind, please be cautious when purchasing!