These units were built in 1990 – 1991 for lightly used suburban services and for strengthening 4-car class 455 units in the peak. They are very similar to class 319 , but using half the traction package and only two motors since it is only 2 cars. Suburban style seating is provided, along with a toilet, but no air conditioning. Since the 3rd rail network operates almost entirely on multiples of four cars the units provide some flexibility to better optimise stock provision to loadings. Couplers are Tightlock, with electrical connections made by jumpers on the cab front, allowing operation with Class 455 units. The units are currently going through a refurbishing programme at Wolverton where they will be repainted into Southern livery.