Size Chart:
US9.5: Shoes Inner length: 6.5"
US10: Shoes Inner length: 6.8"
US10.5: Shoes Inner length: 7.0"
US12: Shoes Inner length: 7.3"
US12.5: Shoes Inner length: 7.6"
US13.5: Shoes Inner length: 7.8"
US1: Shoes Inner length: 8.1"
US2: Shoes Inner length: 8.3"
US2.5: Shoes Inner length: 8.6"
US3.5: Shoes Inner length: 8.9"
US4: Shoes Inner length: 9.1"
This data was obtained from manually measuring the product, it may be off by 1-2 CM