I have to wear orthotics in my shoes or within a day or two I will have a lot of pain in  m feet. Sometimes I can get away without them if if the shoe has really good support.  Typically I wear a Dansko clog around for a house shoe because any slipper I've ever tried does not have enough or the right kind of support--until now.  I can wear these all day with no problem. They are cozy like a slipper, but have the perfect shape and support for my feet.  I love them.  As for sizing, I usually wear a 9.5 in womens, and I have been able to wear a mens 8 in boots.  I wasn't sure what size to order because I think it say their womens 9 was a mens 7. All they had were mens sizes so I ordered an 8 and it fits fine. So being a half size, I erred on the larger size and it worked out for me.