The hull is made of steel.
Early ships were long with a straight-up bridge structure.
Later ships were long with a double-level bridge structure and added 25 mm guns.
AlbaniaAlbania received 3 from the Soviet Union in 1960. One retired in 2011, and the second had retired by 2015.
AlgeriaAlgeria received two from the Soviet Union in 1968. One was cannibalized for parts by 1989. The last was retired by 2009.
BangladeshBangladesh ordered a new ship from China in 1993, based on the Chinese T43 variant, which entered service in 1996. The Tamir-II sonar was replaced by a C-Tech sonar in 1998. It was used mainly as a patrol ship. An order for three more ships was not fulfilled.
BulgariaBulgaria received three short-hulled ships from the Soviet Union in 1953. By 1989, one was cannibalized for parts and another was used as a spy ship. All were retired by 2009.
ChinaThe People's Republic of China received about four short-hulled ships from the Soviet Union in the 1950s. China constructed over 60 of a variant called Type 6610 or Type 010, most of which were of the long-hull type. Production began in 1956 and continued to at least the early 1990s. Some were converted for other roles, including patrol, surveying, submarine rescue, and civilian research.
EgyptEgypt received seven ships from the Soviet Union in the 1970s. By 2015, three were in service with the remainder disposed of.
IndonesiaIndonesia received six ships from the Soviet Union, four in 1962 and two in 1964. None were in service by 1989.
IraqIraq received two ships from the Soviet Union in 1969. None were in service by 2009.
PolandPoland built 12 ships from 1957 to 1962, including four short hulls. Of the short hulls, one was converted into a spy ship, one was retired in 1987, and another was retired in 1988. None were in service by 2009.