First Basements Mitt?

My kid brother's b'day is this weekend and when I asked what he wanted he said a new baseball mitt because his is to small. I went by a store and the guy there said there are 3 different kinds, a catchers, regular and first base. Ryan plays first base but is this guy trying to jerk me around? I never heard of a first basemans mitt being different. Catcher yes, first base no