They came in three basic shapes (octagonal, squat oval and teardrop), three materials (brass, nickel-plated brass and copper-plated brass), with three surface textures (smooth, combed and mottled) and in three sizes (0.75, 1.25 and 1.75 litres). The combination of the parts and the various features yielded a total of 81 possible product variants, of which only 30 went into series production. The electrical connections and heating elements were the same for all three basic shapes, i.e. interchangeable. This modular standardization is one of the fundamental rules of the serial production that would come to prevail in particular in the USA by the end of the 19th century. What was new here was that the designer deliberately took advantage of these necessary structural and manufacturing features. With his building block system, Peter Behrens was putting into practice the kind of standardization he stood up for in the famous Werkbund debate. This concept was so innovative that one can justifiably regard it as the hour of birth of modern industrial design, with Behrens as its father. At the same time, it spelled the entrée of the factory aesthetic into the domestic environment, a process that would later recur several times, for example in the form of tubular steel furniture or the early phonographs from Braun. Behrens drew on traditional forms in the design of his kettle, but freed them from all extraneous ornament. The “honest”, undisguised handling of materials was also important. The new kettle series anticipated the transition from luxury item to consumer object, while also heralding a revaluation, even an exaltation of the industrial form, which now took pride of place on the starched white tablecloth, an effect that would later be echoed in the products of Alfi, Mono or Pott. Priced from 18 to 26 marks, this was by no means a low-ticket item. The Behrens kettle remained in production for around 20 years – another indicator of its design value.