The ideal fit for a cat collar should allow for one to two fingers to fit between your cat's neck and the collar, depending on the size of your cat.
"Slip", "choke", "pinch" or "prong" collars are for dogs only and should not be used on cats.
Some cat owners like to take their cat outside supervised using a body harnesses. Measure your cat's diameter behind his front legs for a good fit. Read more information on choosing a cat harness.
Some cat collars have bells which some cats enjoy. Make sure it is secure and does not come off or can be accidently eaten. The ringing can be pleasant to some cat owners but can can also get on your nerves if you cats plays a lot of the night. Some cat owners like bells on collars of outdoor cats to minimize their ability to catch and kill birds as the bell acts as a "warning".
Don't rely on your cat's collar for identification. If your cat gets lost and slips out of his collar, there will be no sure way to identify him. A microchip placed under your cat's skin by his veterinarian will increase his chances of being safely returned home.