Difference of width, sizing, and footbeds spanning from 37R-39R. NOT A FIT CHECK!!! Just helpful images. USA sizes for me are ugg/adidas 7, Nike 7.5, Vans 8. : r/Birkenstocks
Birkenstock, Papillio, Alpro, And Birki: Brand Q & A – Happy Feet Plus
How to fit your Birkenstocks - Birkenstock Hahndorf