Even while the ships were still under construction, Dutch authorities tried, and ultimately failed, to negiotate purchase orders by interested foreign navies.

[5] However, six decommissioned Karel Doorman-class frigates were eventually bought by the Belgian, Chilean, and Portuguese navies, and the proceeds were subsequently invested in development of the Holland-class offshore patrol vessel.

Air defence is provided by an AIM-7 Sparrow medium-range semi-active radar homing air-to-air missile with a range of up to 14 kilometres (8.7 mi) Sixteen VLS cells are mounted on the port external bulkhead of the hangar.

The Goalkeeper close-in weapon system provides close-range air defence and can fire up to four thousand 30 millimetres (1.2 in) rounds per minute at a range of 200 to 3,000 metres (660 to 9,840 ft).

In 2004 two ships, Tjerk Hiddes and Abraham van der Hulst were sold to Chile and renamed Almirante Riveros (FF-18) and Blanco Encalada (FF-15) respectively.

On 21 December 2005, Karel Doorman and Willem van der Zaan were sold to Belgium and renamed Leopold I (F930) and Louise-Marie (F931) respectively.

[3] The Royal Netherlands Navy and the Belgian Naval Component decided to upgrade the four frigates by rebuilding both hangar and helicopter deck for the NH90 NFH helicopter as well to replace the forward mast for fitting the new Thales SeaWatcher 100 phased array surface search radar and Gatekeeper electro-optical surveillance system.

The system automatically detects and tracks asymmetric threats and very small objects such as swimmers and periscopes in all weather conditions.

Seastar is internationally marketed as Sea Watcher 100 Gatekeeper is a 360-degree panoramic electro-optical surveillance and alerter system based on IR/TV technology.

Designed to counter emerging asymmetric threats down to small boats and swimmers, Gatekeeper increases short-range situational awareness in littoral environments.

This means that anti-air equipment also has to be present, in the form of VLS (vertical launch)-cells carrying Standard Missile 2 or ESSM-projectiles.