These serials were changed on 13 July 1915 to G.33/15 - G.38/15, for unknown reasons and again on 6 November 1915 to R.2/15 - R.7/15 in the R (Riesenflugzeug - giant aircraft) series, adopting the R.II to R.VII designations.

[2] As designed, the R.II was a large three-bay biplane with unstaggered wings of unequal span[6] and a fully enclosed cabin.

[7] The main undercarriage consisted of divided units, each of which carried dual wheels, and the tail was supported by a pair of tailwheels.

[8] The fuselage was forked into an upper and lower section, which allowed a clear field of fire to the rear of the aircraft.

[11] During its acceptance flight, the newly refurbished R.II carried a 2,310-kg (5,100-lb) useful load to an altitude of 3,800 m (12,500 ft) and stayed aloft for four hours.