My wife received these for Christmas and we had to return them because one slipper developed a ridge across the arch.  At first, they were fine, but within one day, a pronounced ridge developed in the sole that felt like possibly a joint of two pieces of material was overlapping.

After receiving the replacement pair, there were no issues for about two months, then without any warning, the same ridge developed.  We will probably return these to Isotoner as we can no longer return them to Amazon.  These slippers were only worn indoors on mostly carpeted floors.

Warning: the Isotoner warranty on these slippers is one year, but you have to pay to ship the slippers to Isotoner and you have to include $5 (presumably to cover return shipping).  IMO, that is a crappy warranty.  They should at least cover shipping one way as the cause of the problem is the material in the slipper, not the way it was used.

We will not buy another pair of these slippers.