Crocs Women's Kadee Flat, Black/Black, 4 M US

Would they be comfortable for someone that suffers from planter fascitis?

How do choose a size? It's just add to cart, I can not find any information in the description nor the chart someone mentions in the Q&A.

I was thinking of purchasing these as a gift for my friend who has a narrow foot, how wide do these run?

Description doesn't give size. What size are these for?