[1][2] These were Maximum Traction bogie tramcars of the drop-end-and-centre design (precursors of the Melbourne W class trams), with four doorways in the open centre (smokers') compartment as well as one at the front and another at the rear; each of the two passenger saloons featured four side windows.
The cars were very similar to trams built by Duncan & Fraser for the contemporary Prahran & Malvern Tramways Trust (P&MTT) in 1913/14, which had three saloon windows, a larger smokers' compartment, and three centre doorways.
As a trial for what became the P class trams, one car (number 20) was fitted with air-brakes and the large roof-mounted cylindrical destination displays, which were unique to the HTT.
After the M&MTB take-over, the original HTT French grey livery was replaced by a brown colour scheme and fleet number of each tramcar was increased by 106; a simplification of the alphanumeric classification scheme saw the whole class being added to the C class (which had originally been allocated to the 1913 P&MTT Maximum Traction bogie trams).
Tramcars that survived to serve during World War II had their rear doorways blanked-off as a safety measure.