[1][a] The weapons systems, with the exception of the Sea Sparrow surface-to-air missile (SSM) were French.

The radar and tactical data systems were Dutch and the hull and machinery were constructed in Belgium.

[1] The frigates feature an action information centre between decks and the ships could be split into two independent gas-tight citadels in the case of nuclear, biological or chemical warfare.

[2][c] The class was fitted with two eight-barrelled Corvus chaff launchers, a Sagem Vigy 105 optronic director, a Signaal DA-05 air/surface search radar, a WM-25 surface search radar, SQS-510 hull-mounted sonar, and the SEWACO IV tactical data system with Link 11 capability.

They were also given Argos AR 900 intercept electronic support measures and SLQ-25 Dixie torpedo decoy system.

[3] The construction programme of four ships was approved on 23 June 1971 and an order was placed with two Belgian shipyards in October 1973.

[3] Westhinder was damaged during an anti-submarine exercise off the coast of Norway in September 1988, striking a rock.

[7] Bulgaria joined NATO in 2004 and sought out options to replace their older Soviet-era fleet to fulfill their obligations with the organisation.

[9][10] In 2011 Drazki took part in NATO operations against Libya and since then, the vessels have participated in several naval exercises with Turkey.