 The locomotives were ordered by the New Zealand Railways Department (NZR) in 1880, and delivered from the Avonside engine works in 1881–1882.They were considerably larger than the earlier R class, and all saw service in the Wanganui district, with its abundance of sharp curves and grades.These two classes of Single Fairlies were considerably more popular with the engine crews than their older Double Fairlie counterparts, which often suffered frame breakages whilst operating in the Wanganui district.