In practice they were not strong enough for open ocean operations and were reclassified as 1st class torpedo boats.

They were built by six different yards (thirteen by White at Cowes, nine by Thornycroft (five at Chiswick and four at Woolston, Hampshire), four each by Denny at Dumbarton and by Hawthorn Leslie at Hebburn, and three each by Yarrow at Cubitt Town and by Palmers at Jarrow).

These vessels closely resembled the earliest 26-knotter TBDs of 1892–93, having 'turtle-back' forecastles and carried a similar armament.

[5] Armament consisted of two 12-pounder (76-mm) 12 cwt guns[b], and three 18-inch (450 mm) torpedo tubes (in three single mounts).

The machinery was similar, but was rated at 3,750 shaft horsepower (2,800 kW), with a speed of 26 knots (30 mph; 48 km/h) specified.