See this link. I actually thought it was just a cool pillow. I didnt realise it was like a cool pack placed on top of a pillow. Somehow I get the the impression of sleeping on a rubber ring or arm band type material .
Not too sure now.
I've purchased one and to be honest I just couldn't sleep on it. It is covered in kind of a plastic cover similar to the type of material that arm bands are made of on one side and a kind of velvet type feeling on the other (found that side warm), the inside is a sponge, you pour water in and it soaks into the sponge. I tried using it on a number of occasions but just found it too uncomfortable to sleep on even after putting it inside a pillow case and the cover smells stink.
Save your money as far as I'm concerned, what i've done is put 2 extra pillows at the end of the bed and rotate them during the night.