The Austro-Hungarian Navy, after competitively evaluating six submarines of three foreign designs, selected the Germaniwerft 506d or Type UD design over a design from Whitehead & Co. for the U-7 class. The boats, numbered U-7 to U-11, were designed to be 69.50 m (228 ft 0 in) long and displace between 695 and 885 tonnes (684 and 871 long tons) when surfaced and submerged. They were to be armed with five torpedo tubes and a deck gun.