They were all named on 18 June 1651 as Pearl, Mermaid, Primrose and Nightingale.They were of 286 tons, and each was established with 22 guns and 100 men.

The "one ship" was the Second rate Antelope ordered on 8 August 1651 to be built by Master Shipwright Christopher Pett at Woolwich, originally to carry 40 guns and to be 110 ft keel length, 32 ft breadth and 18 ft depth in hold (thus intended to have a burthen of 59914⁄94 bm tons); on 1 October the Council agreed to a request from its own Admiralty Committee that Pett be allowed to build his frigate "to his own dimensions", and also that she may carry 50 guns.

Finally, the Admiralty Committee issued an Order on 5 December 1651 to also build three small vessels "to ply among the sands and flats to prevent pirates".

These three were the Drake, Merlin and Martin, which were of varying dimensions and tonnage, but were all built in the state dockyards and established as Sixth rate vessels to carry 14 guns and 90 men apiece.

The dimensional data was so varied that it will be listed on the individual vessels along with their gun armament composition.