The inner length of size 16 is 11.5cm, the inner length of size 17 is 12cm, the inner length of size 18 is 12.5cm, the inner length of size 19 is 13cm, the inner length of size 20 is 13.5cm,
The inner length of size 22 is 13.5cm, the inner length of size 23 is 14cm, the inner length of size 24 is 14.5cm, the inner length of size 25 is 15cm, the inner length of size 26 is 15.5cm
