In addition to showing the flag, the ships fought pirates and suppressed the slave trade in East and West Africa.

These ships were designed by Sir Edward Reed, the Director of Naval Construction, as replacements for the various gunvessels built for the Crimean War.

Combat experience against Chinese fortifications had shown that the single 32-pounder smoothbore armament of the earlier ships was not powerful enough so Reed was directed to prepare a twin-screw, shallow draft design suitable for riverine operations that incorporated a pair of steam engines from the older gunboats, a heavy armament, and enough freeboard to allow for service at sea.

If they ran aground, this shape allowed them to be pulled off easily and they remained upright if stranded by a receding tide.

[5] The class was barque rigged and their best speed under sail alone was over 12 knots (22 km/h; 14 mph) if running before the wind, despite the drag of the propellers, which could neither be hoisted out of the water, nor feathered.

Gnat's service, however, was rather short as she ran aground and was wrecked on Balabac Island, south of the Philippines, less than a year after she was commissioned.

Another major deployment area was the Gulf of Guinea in West Africa where Fly, Lynx, Flirt, Dwarf, Beacon, Avon, Pert, Growler, Rocket, Hart, and Boxer all spent part of one or more commissions.

Beacon supported British coastal operations during the Third Anglo-Ashanti War in 1873 while most of the others engaged river pirates at various times.

Rocket, Elk, Dwarf, Beacon, and Avon served at least one commission off the south-east coast of South America, while Cracker spent her entire career there.

Dwarf made a port visit to Asunción, on the Paraguay River, some 600 miles (970 km) from the ocean during one of her tours in the region.

The machinery of Avon, Dwarf and Elk was in good enough shape that they were assigned as tenders to the coastguard district ships at Hull, Southampton, and Liverpool for a number of years.