Usually with Authentics, there is a breaking in period but these are already so soft and comfortable. I ordered a half size down and they fit perfectly. The only thing that feels a little weird is the fabric at the heel doesn’t come up as high on my heel as my other pairs, but I’m wondering if that is from the ultra cushion bottoms. Hopefully they will pack down some with wear! I tied them a little bit more snug and they don’t feel like they will fall off my heel.