very wide, I wear a narrow but also have to put an orthotic arch support in.  I thought the insole would come out, so I could put mine in, but it was not removable.  Also the lining in the heal area started to tear at the seams.  But my foot is so narrow, I have to wear a thick sock with it too. So I had another pair of Vionic winter slippers that had a removable furry insole. I put those insoles, in on top of the ones that were already in these, and it worked pretty well.  Not for a narrow footed person. But then again, I am used to nothing fitting properly with a narrow foot.  So giving 4 stars.