I wear a size ten and a half and they fit like a glove but I think they will be tight on the leg of the size eleven and a half. They are very comfortable and are suitable both for relaxing in the house and for leaving the house for a few hours. I wouldn't wear them unless I had a full 8 hour day with lots of trips planned. But they will probably be able to be worn all day, they might not be the best choice for that. There is a lot of support when walking and they have a thicker sole than many slippers. They just don't quite compare to a pair of Vans loafers in terms of outsole thickness. But they are equal in overall quality, which makes them worth their price, even if it's a bit steep for a pair of shoes designed for indoor use.