This is a bad collar for a cat. Here’s a flea collar. I think you should avoid. We had a cat into the office and it had some kind of collar on. I think it was a flea collar. But it’s just engineered out of a cable tie. It has the ability to get tighter, but it does not have the ability to get looser.
And you can see in one of the pictures. It was already chewing on the free end of the cable tie. If another animal came up and grabbed the end of the cable tie, it could cinch that down on the cats neck, fatally.
The owner just doesn’t know better. But the manufacturer obviously does not care. “Get the product out there. Just sell them.”
Why not take a look at your cats flea collar, and see if it’s just a cable tie. Sure, it might have chemicals in it, but just make sure it can come off if he gets his neck hung up on something. And make sure that if a dog grabs it, it can’t be tightened, fatally.