As with most other Drummond productions, the locomotive had two inside cylinders and Stephenson link valve gear.

The boiler was interchangeable with the T9 class, and likewise was equipped with water tubes fitted across the firebox combustion space, with the aim of increasing heating surface whilst facilitating water circulation; this device however also increased maintenance costs and was soon removed by Drummond's successor, Robert Urie.

When transferred to Southern Railway ownership after 1923, the locomotives were outshopped in Richard Maunsell's darker version of the LSWR livery.

[2] The LSWR standard gilt lettering was changed to yellow with 'Southern' on the water tank sides.

However, thirteen of the locomotives had been withdrawn by the end of 1948, resulting in gaps in the sequence.