Junkers continued to believe in the monoplane layout constructed entirely in metal, and continued the J-series with a number of newer monoplane designs. One of the most successful was the all-duralumin J 7 technology demonstrator aircraft prototype, which went through five major and minor changes in its airframe design during tests throughout 1917 and which was later stretched to form the two-seat J 8. The J 8 was the first cantilever monoplane design, and looked extremely "modern" when compared to contemporary wire-braced biplane designs. The J 8 was put into limited production by the Junkers-Fokker Werke (a collaborative firm founded through strong influence of the German government on October 20, 1917) as the J 10, receiving the "IdFlieg" designation of CL.I, a small number of which saw service on the Eastern Front just before the war ended. Likewise, the single-seat J 7 itself led to the J 9 design, built in small numbers as the Junkers D.I low wing fighter by both the Junkers firm itself (abbreviated "Jco" or "Jko") and the Junkers-Fokker-Werke AG (abbreviated "Jfa") — with the resulting three-letter abbreviation of either firm usually marked on the J-9's landing gear wheel covers.