This collar magically adjusts it's size to fit comfortably around the neck of a familiar. It can take on whatever appearance the caster desires. 

While wearing this collar, the familiar does not need food, water, air, or sleep.  If the familiar drops to 0 hit points or is temporarily dismissed, any items it is wearing or carrying are transported to the pocket dimension with the familiar and return with it.  If it is permanently dismissed, any items it is wearing or carrying appear next to the caster.