The class varied from K V-class submarine due to the removal of two external torpedo tubes, which were removed to reduce the boats' vulnerability to depth charging.

The boat had a diving depth of 50 metres (160 ft).

K VIII-class submarine was built after the John Philip Holland design.

[1] All ships were still in service at the start of World War II.

During the war K IX was transferred to the Royal Australian Navy and renamed K9.