The South West Trains (SWT) Class 458 (or 4JOP) outer-suburban electric multiple units were built by Alstom at Washwood Heath between 1998 and 2002. The 30 four-car units are part of Alstom's Juniper family of trains, which also includes Classes 334 and 460.These trains have been used by SWT since they were built. Since 2013 they are being merged with the mechanically similar Class 460 fleet and reconfigured into 36 five-cars units, which are being designated Class 458/5.