FPNI. Most of the cats I’ve had wouldn’t/won’t wear collars. They’ve lost the collars I’ve tried to get them to wear. I did try to use break-away collars, or collars that had elastic inserts. I’ve given up on collars for them. I have them microchipped, though. The city where I live doesn’t require collars/tags for cats as long as they’re licensed and microchipped.