
I have some and find them useful for car journeys on hot days. However,
these are fantastic if you want to create a permanent cool spot in the house for them to lie :) My Newfie loves hers an sleeps on it all year round.
They are pricey and I haven't been able to locate them in the UK so had to buy one from the US which made it even more expensive but, IMO, worth every penny :)
You can buy the ones that you have to soak
here (scroll down the page)