This shoe is a good wide fit (got the 4E).
Unfortunately, the design of the shoe's tongue is such that as you walk, the tongue edge presses against the ankle, causing too much discomfort which would eventually be painful.
Had to return it.

A shame because otherwise it fits well - but buyers should make sure that they don't encounter the same problem.

Went back to the model 647 (MX647BK) although it is not "duck-billed" like the 577 and hence a little tighter around the tip of the toes..
The best model I've worn was the CM323BY which they don't make anymore.