Two boats (U-107 and U-108) were laid down in early 1918 by Ganz Danubius in Fiume, but neither was launched or completed before the end of the war.

The design for the U-107 class was similar to the Germaniawerft UD design,[1] which had formed the basis of the Austro-Hungarian U-7-class boats that had been ordered in 1913 and had been sold to the Imperial German Navy in the early stages of World War I.

[2] According to Conway's All the World's Fighting Ships 1906–1921, the specifications of the U-107 class are very unclear.

For propulsion, the design featured two shafts, with twin diesel engines of 2,300 bhp (1,700 kW) (total) for surface running, and twin electric motors of 1,260 shp (940 kW) (total) for submerged travel.

Regardless of the number planned, Conway's reports only four boats had any sort of construction activity.