Probably good for dogs but even the smallest one is far too big for a cat. The smallest is 7" but the Bite-nots are 2.5" for cats unde 10lb or 3" for cats over 10lb.
Bitenot are measuring differently though Mark, 2.5 inches is the height of the collar - not circumference. These inflatable ones are measuring the circumference like you would a normal collar. VetUK sell the extra small ones (7-9") which are cat sized. Thanks for linking to these Debsy, they are loads cheaper than a Bitenot and actually available in the UK.
There was a post the other day where someone's cat was getting the Elizabethan collar off, I was going to say about Bite-Not but knew you couldn't get them in the UK anymore. Will find the post and link to this thread