The Highland Railway Cumming 4-4-0 class was a pair of 4-4-0 steam locomotives designed by Christopher Cumming the Locomotive Superintendent of the Highland RailwayThey had 20-by-26-inch (510 mm × 660 mm) outside cylinders with Walschaerts valve gear 6 ft 3 in (1.905 m) driving wheels and a boiler pressed to 175 lbf/in2 (1.21 MPa).