Size Reference 21 size inner length approximately 13.5cm, 22 size inner length approximately 14cm, 23 size inner length approximately 14.5cm, 24 size inner length approximately 15cm, 25 size inner length approximately 15.5cm, 26 size inner length approximately 16cm, 27 size inner length approximately 16.6cm, 28 size inner length approximately 17.3cm, 29 size inner length approximately 18cm, 30 size inner length approximately 18.7cm Size Reference The inner length of size 21 is approximately 13.5cm, and the inner length of size 22 is approximately 14cm The inner length of size 23 is approximately 14.5cm, and the inner length of size 24 is approximately 15cm The inner length of size 25 is approximately 15.5cm, and the inner length of size 26 is approximately 16cm The inner length of size 27 is approximately 16.5cm, and the inner length of size 28 is approximately 17cm The inner length of size 29 is approximately 17.5cm, and the inner length of size 30 is approximately 18cm