Based on the basic Derby high density design, the sets are similar to Class 127 but were internally superior as the class had larger windows, better furnishings, lighting and wall surfaces. Some sets were also built for the CLC line between Liverpool and Manchester. These were later transferred to Marylebone. They also worked from Tyseley in the later years. The final Class 115 working out of Marylebone was in July 1992. The Tyseley sets survived a bit longer, until February 1994.