Classification of Ready Mix Concrete as excisable distinguishes factory premix from exempt site-manufactured concrete for duty purposes. Ready Mix Concrete, produced in factory-like plants with centralized crushing, automated batching, silo-fed cement, metered water and admixtures and delivered in a plastic condition by transit mixer, is an excisable product classifiable under the Central Excise Tariff, whereas concrete mixed at the construction site by conventional on-site methods for use at that site is exempt under the relevant notification.