I have a 12lb pomeranian and he loves these. I give him one everyday when I get home from work...he grabs it with his tail wagging and runs in the bedroom to eat it so no one "steals" it :)
He is around 8 years old and his teeth are sparkling clean. I use these in addition to brushing and scraping the tartar, once every few weeks. I don't brush his teeth as often as I should so I feel like these are a great supplement in between brushings/scrapings.