I had Kaji micro chipped when he was neutered. I hope he was still out when they did it, otherwise the thought of that makes me cringe. I know they advertise that it's as small as a regular injection, but Kaji had a bit of a obvious wound on his back. I put ointment on it (neosporin) because it looked very raw. He's fine now (7 months later) and has no scab or anything. I'm glad I won't have to do either again.