If they are the ones that you wet yourself and they expand, my friend bought one. Her bc didn't like it too much but I think she did get used to it. Not much help, am I? :-D
I have two & one is always in the car when we go to shows in the summer, my cavaliers like it & along with using fans & the cars air con hardly pant at all & seem to keep very cool no matter how hot it gets
You fill them with water & the actual bed itself is plastic & does not expand but the filling makes the bed conform to the dogs shape. It's the one bed my cavaliers don't dig up