Purchased these to replace the Tamarac slippers I ended up returning. These slippers cost a little more but they are MUCH more comfy and they are quiet, (the Tamaracs were very noisy on hard floors). He is a street shoe size 10.  I ordered the slippers in M (10.5-11.5) and they fit great!  My BF is very happy with these slippers and I'm about to order myself a pair!