This paper describes the first method for making nanodisks having similar aspect ratios and differing by their size. Flat, single-crystal silver nanodisks in equilibrium with spheres are produced using colloidal solutions. The nanodisk size is tuned by the relative amount of reducing agent involved in the synthesis whereas their aspect ratios remain the same order of magnitude. The 3D nanodisk shape is determined by transmission electronic microscopy using the weak-beam dark-field technique. These nanodisks characterized by such anisotropic shapes exhibit several plasmon resonance modes observed in the UV-visible range.