27 C.F.R. § 40.215

Every package of cigarettes shall, before removal subject to tax, have adequately imprinted thereon, or on a label securely affixed thereto, the designation “cigarettes”, the quantity of such product contained therein, and the classification for tax purposes, i.e., for small cigarettes, either “small” or “Class A”, and for large cigarettes, either “large” or “Class B”.