 They can be coupled to a Duplex set.The Eurostar train is essentially a long TGV, modified for use in the United Kingdom and through the Channel Tunnel.Differences include a smaller cross-section to fit within the constrictive British loading gauge (though High Speed 1 can accommodate Berne gauge traffic, this feature was required when Eurostar trains operated on existing main line tracks from London Waterloo to the Channel Tunnel), British-designed asynchronous traction motors, and extensive fireproofing in case of fire in the Channel Tunnel.