This is the most comfortable Birkenstock style Ive ever found, the Arizona in suede leather with soft footbed.  I size down in these. My normal shoe size is 8 and my foot is slightly narrow.  I get these in 38N and they are a perfect fit.  I have them in three colors now and they are the only shoes I want to wear.  Bend them before wearing to give them a slight curve, and, for me, they are comfortable right out of the box - no break-in period.