About the size: The size chart (EU Size) can be checked in the photos.
Zori vs Geta Simply speaking, zori are formal sandals, while geta are casual. Zori are always worn with tabi socks, which is why they are not usually the choice for a yukata outfit, when tabi socks are not worn. Traditionally, zori are usually worn with kimono at very formal occasions like weddings. But is not a hard and fast rule. You can still choose to wear zori with yukata if you prefer a softer sandals.
