17.6cm inside size 28

18.3cm inside size 29

The inner length of size 30 is 19cm

The inner length of size 31 is 19.8cm

20.4cm inside size 32

21.1cm inside size 33

22cm inside size 34

22.5cm inside size 35

Inner length 23cm in size 36

The inner length of size 37 is 23.5cm

Size 38 inner length 24cm

The inner length of size 39 is 24.5cm