I have worn Birkenstocks for 20 years and they are the best shoe. I love the Zurich style but the oiled leather and wool combination for these uppers is not good because it is to stiff and never breaks in.  I got the Iron Oiled Leather with Grey Wool. They don't bend at the toe or the top of the ankle causing pain on the top of the foot and strangely the calf. It did not get better over a few weeks so I sent them back.  I would like to try the Zurich in the suede or oiled leather though they are cute!