5.5M is my usual size but I felt this size in this boot was smaller and narrower than usual. Being non leather I feel it won't stretch out much so if you have a wide foot you might have problems . The calf didn't quite fit and I couldn't do the zip up full. Don't have skinny stick legs but not fat either so the side buckle won't help much for wide calves. Once I got it done up it was a very tight and uncomfortable feeling around the calf just below the knee. I persevered and added socks and there was a bit of stretch. But then I decided to scrunch the boot down a bit along the leg and it relaxed it a lot and now it's not too bad. The sole is excellent and non slip including the heel. Heel height not quite the 2 inches.
If you get this boot to fit you in all areas it will be a reasonably comfortable casual boot.