I usually require a 10 in some of Clark's lines., although  I wear 91/2 N in most shoes.  I took a chance on this 91/2 M, since it was their was not a 10 available.  The fit was perfect.  I sometimes wear a store-bought or prescription orthotic and there is room for that, but I don't think it will be necessary as the support is excellent.  The boot appears very well-made and is dressy enough to wear with skirts, etc.  Very versatile.