Birkenstock don't oil their "oiled leather" properly. I grew up oiling horseriding saddleware and Birkenstock's "oiled leather" is dry & hard, not supple & soft. I do it myself. These are "Franca"
Birko Flor Vs Leather: What Is The Difference?
Womens And Mens Birkenstock Arizona Habana Oiled Leather - Happyfeet.Com