[1][2][3] The Types ZA and ZB tenders were both introduced in 1892 as tenders to the original Cape Government Railways (CGR) 7th Class 4-8-0 Mastodon type locomotive, which was built in two batches.

Since a Neilson works picture shows one of the Neilson-built batch of locomotives with a three-axle tender, it is likely that the larger-capacity Type ZB three-axle tenders were delivered with the second batch of 32 7th Class locomotives, built by Neilson.

These engines would be designated Class 7 on the South African Railways (SAR) in 1912.

[1][2][3] The tender had a coal capacity of 5 long tons (5.1 tonnes) and a water capacity of 2,370 imperial gallons (10,800 litres), with an average maximum axle load of 9 long tons 13 hundredweight 3 quarters (9,843 kilograms).

The 32 Neilson-built tenders should have been numbered in the SAR number ranges from 954 to 967 and 975 to 977 in respect of the seventeen ex-Midland System engines, and 970 to 974 and 978 to 987 in respect of the fifteen ex-Eastern System engines.