A cat's collar should reflect the investigative behaviour displayed by cats. Most cats climb and jump, which may put them at risk of becoming caught or hooked by obstacles such as tree branches, nails, and fences. An elasticised collar will help the cat disentangle itself from any danger. If you can place two fingers snugly under the cat's collar, then it's a good fit.
Dog collars and leads
A soft, flat collar is a sound choice for most dogs. It may be made of leather or a weaved, webbing type material. The collar should reflect the size and strength of the dog and fit comfortably. The clasp or buckle should be comfortable and not dig in or rub the pets' skin. When fitting a collar to your dog, you must ensure it is firm enough that your dog will not "slip" it and take off, yet you must be able to fit three fingers snugly underneath to allow comfort and adequate breathing ability.
For strong dogs or dogs that pull on a conventional collar, there are numerous head halters available. If applied correctly a head collar will tighten around the dog's muzzle when the dog pulls. The dog does not favour this, and therefore he or she should walk beside you in a calm and relaxed manner. These types of restraints do not inflict pain or injury to the dog.By Lauren- Vet Nurse