@swimma26 That's a good question...is 3 1/2 a people blade maybe? When I think of a 3 blade for grooming I think of the 3 3/4 (13 mm). Amazon reviews for the 3 1/2 show people using it for humans and dogs so honestly I don't know.
EDIT: NEVERMIND I FIGURED IT OUT!! So most andis blades will...