If your kid's foot length is 15.5 cm, then add 1 cm ~ 1.5 cm, you need to choose the size which insole length is 16.5 cm ~ 17 cm.
Size 6 = CN size 21 = insole length 13 cm, fit for foot length 12 cm
Size 6.5 = CN size 22 = insole length 13.5 cm, fit for foot length 12.5 cm
size 7 = CN size 23 = insole length 14 cm, fit for foot length 13 cm
Size 8 = CN size 24 = insole length 14.5 cm, fit for foot length 13.5 cm
Size 9 = CN size 25 = insole length 15 cm, fit for foot length 14 cm
size 9.5 = CN size 26 = insole length 15.6 cm, fit for foot length 14.6 cm
Size 10 = CN size 27 = insole length 16.2 cm, fit for foot length 15.2 cm
Size 11 = CN size 28 = insole length 16.8 cm, fit for foot length 15.8 cm
size 11.5 = CN size 29 = insole length 17.4 cm, fit for foot length 16.4 cm
Size 12 = CN size 30 = insole length 18 cm, fit for foot length 17 cm
