Ten Type XM tenders entered service in 1913, as tenders to the Class 4A 4-8-2 Mountain type steam locomotives which were acquired by the South African Railways in that year.

[1][2][3] Type XM tenders were built by the North British Locomotive Company in 1913.

[1][2][3] The Type XM tender had a coal capacity of 8 long tons (8.1 tonnes), a water capacity of 4,000 imperial gallons (18,200 litres) and a maximum axle loading of 11 long tons 18 hundredweight (12,090 kilograms).

[3] A number, when added after the letter code, usually indicates differences between similar tender types, such as function, wheelbase or coal bunker capacity.

Early versions of the built-up coal bunker sides were in the form of a slatted open-top cage, made of rectangular steel rods.