TT for sure! The Innotek I had was garbage and went in the trash in less than a year. He may need an ecollar with long points for a dog as big as a Mastiff and they need to be fairly tight to have good point contact. The kids had a Mastiff (Ben!) that was a gentle giant and wouldn't harm a flea, but they are so big I don't know whether that choke collar would do much other than get you dragged to death, LOL!