Thanks for the links, very helpful.
I have neuropathy and was getting very swollen legs and ankles during the hot weather. I bought one of these to sleep at night and even doubled the height with a firm cushion underneath (taken from an armchair). This raises the legs pretty high, and means you have to sleep on your back, but it has really helped reduce the swelling.
As soon as I get up I wear compression stockings, which I leave on all day. Okay, they are uncomfortable during hot weather but not as uncomfortable as having horribly swollen legs which can be so painful.
Between these two things my legs are not nearly as bad as they were.