I have them but word of caution. They have a short life in bed. A few hours at most. They do draw heat away quickly but don't expect all nite relief as they don't provide it. If it's oppressive, shove the gel mat into a freezer 45 mins before retiring
They are OK, but I wouldn't use the pillow one again. I think the cooling effect may have been part of the cause of me losing large clumps of hair 3 years ago. I was under a lot of stress at the time, but that's nothing new and have I never lost hair through stress before or since. It may be just a coincidence, but I thought I should share my experience.