When our 2 cats where little we took them to a nearby Vet to get them fixed and chipped ,my wife had used these Vets to treat our 2 American short hairs , the afternoon when they came home the female wanted to be left alone and the male came over to me for a pet and I felt a lump in the middle of his back 1 inch to the right of his spine and a swelled up line from the back of his neck. I was mad !!! I called the vets office and they told me chips can shift , the chip had only been in for a few hours, I told them I was going shift to another vet and they said to keep everyone happy they would remove the chip no charge, I would just pay the hospital bill, I refused and told them what I thought. The next day I call another Vet who we use now, our new Vet examined Cody and found the lump and scanned it and said there is no reading and this is a universal scanner, x ray showed something and she took it out the next day and chipped him ,they have a operating room and she called me the next day and said Cody is doing well but he is a devil, he was able to dump his litter box of the floor during the night. She wanted me to meet her at Metro animal hospital with our female so she could scan with the hospitals equipment and found a Home Safe chip, so this makes me think not all scanners will read all chips. No body wants to lose their cat and we have had a few close calls , we watch our male SV anytime a door is open , sick cats and lost cats are always bad news.