The Talmud talks of a minimum of 3x3 fingerbreadths in defining a garment. Tosafot (Shabbat 26a, s.v. ein) point out that this is assuming the garment does or will include more material. If the entire garment. R. Natan Gestetner (Resp. L’Horot Natan, XI, 133) considers this point in explaining the suitability for a small belt buckle in effecting a “kinyan chalipin”. Even though the length alone may be 3 fingerbreadths and not the height, the buckle is made that way to begin with. Further, it seems indicated that the 3x3 requirement is only for a garment. Other utensils qualify based on the independent standards of that utensil.