In 1903, the CGR placed six Type B locomotives with eight-wheeled bogie tenders in service on the Avontuur narrow gauge line in the Langkloof. They were built by W. G. Bagnall and had bar frames, copper fireboxes and Stephenson valve gear. In 1912, they came into SAR stock and, in 1914, a further three locomotives with slightly longer boilers were acquired by the SAR. One of these was also built by Bagnall while the other two were built by Kerr, Stuart and Company. These three were commonly referred to as the Improved B. When a system of grouping narrow gauge locomotives into classes was eventually introduced somewhere between 1928 and 1930, they were to be classified as Class NG8 but had already been withdrawn from service.