I know that there are different companies who supply the microchips. The ones my vet uses are inserted with only 20g needles and the chip itself is microscopic and can't be felt. The number of the microchip is stored with the company who supplies the microchips, but unless you pay an extra amount ($25-$50) it is the veterinarians name/number/address that is stored in the computer. Therefore if you move over the years, you would need to notify your vet rather than to notify the microchip company. A side note: we're also finding that most microchips (inserted in the scruff of the neck of cats, dogs, rabbits and ferrets) travel down under the skin to the belly area. (Important to let the people who are scanning stray animals know that this occurs.) Sandi Best Little Rabbit, Rodent & Ferret House Seattle, WA [Posted in FML issue 1998]