23 is one size larger (inner length 15.5cm), 24 is one size larger (inner length 16cm), 25 is one size larger (inner length 16.5cm), 26 is one size larger (inner length 17cm), 27 is one size larger (inner length 17.5cm), 28 is one size larger (inner length 18cm), 29 is one size larger (inner length 18.5cm), 30 is one size larger (inner length 19cm), 31 is one size larger (inner length 19.5cm), 32 is one size larger (inner length 20cm), 33 is one size larger (inner length 20.5cm), 34 is one size larger (inner length 21cm)