Visitor Oyster cards are plastic smartcards you can use instead of paper tickets. Put on pay as you go credit which you use when you travel. It is the cheapest way to pay for single journeys on bus, Tube, tram, DLR, London Overground, TfL Rail and most National Rail services in London.
You can use your Visitor Oyster card to pay for travel to Heathrow Airport (TFL rail and Heathrow Express) and Gatwick Airport (train services and Gatwick Express).