Universal boats of the KFK (Kriegsfischkutter) type were developed in late 1941 on the basis of a fishing seiner. They were built by various companies in Germany and other countries (including neutral Sweden). After a small reequipping, they could be used as trawlers (they could carry contact, magnetic, and acoustic trawls), submarine hunters (a hydroacoustic station was installed on the boats), or patrol boats. The boats' hulls were made of wood, but some shipyards made them of metal or composite according to their technological requirements.

The basic armament included 20-mm or 37-mm guns, mounted on a platform in the bow and on top of the wheelhouse. Over time, armament options changed and could include one 37-mm and up to six 20-mm automatic guns