[1] The ships, with a diving depth of 60 metres (200 ft), were used for patrols in the Dutch home waters.

O 12 entered German service in 1943 as UD-2.

The ships were built by two shipyards.

O 12, O 13 and O 14 were built by Koninklijke Maatschappij De Schelde in Vlissingen and O 15 in Rotterdam at Fijenoord shipyard.

German Navy: 30 January 1943