The OB has a wheelbase of and is a semi-forward control model designed to carry 26 to 29-passenger bodywork.
It is fitted with a petrol engine and has a 4-speed gearbox and fully floating rear axle. The brakes are of the vacuum servo assisted hydraulic type.
Although only 73 were built prior to the cessation of production due to World War II, it reappeared in an unchanged form at the end of the war, continuing in production until 1950. A total of 12,766 were produced making it one of the most popular buses of its type ever.