Fare zones 7–9 are ancillary zones of the Travelcard and Oyster card fares scheme managed by Transport for London, used for calculating fares from some stations outside Greater London that are not in zones 4, 5 and 6. Travelcards are available on Oyster with validity in these zones. They are not included in the validity of National Rail out-boundary Travelcards unless mentioned in the Route section as "AAA LDN ZONE 7-9". Fare zones 10–15 (or A–F by their hexadecimal number) have fares set by National Rail train operating companies and the zones themselves are not publicised. The fare zones are outside Greater London, typically more than from Piccadilly Circus. Scope The zones extend in segments from the boundary of Greater London to the north and west into Hertfordshire and Buckinghamshire, to the east into Essex and Kent and to the south into Surrey and West Sussex. Unlike zones 1–6, they do not form complete rings around London but rather patches. They include eight London Underground stations on the Metropolitan line and London Overground stations. Zone 7 Zone 7 consists of the Hertfordshire stations on the Metropolitan Line and the first London Overground and West Anglia Main Line stations outside zone 6. Zone 8 Zone 8 consists of , the remaining London Overground stations where TfL set fares, and stations in Kent where Oyster is valid. Zone 9 Zone 9 consists of , and . and are technically in this zone (for capping purposes only), but not publicised as such due to cheaper paper fares on weekly, monthly and annual tickets. The following stations are within zone 9: Special Zones These zones have their fares set by National Rail companies. Zones are referred to by their decimal or hexadecimal number. Zones are allocated corridors extending out from London, rather than the roughly concentric circles that the non-special zones have. Zone 10, or Zone A consists of (sometimes called Zone W), and c2c stations out to (sometimes called Zone G) Zone 11, or Zone B, consists of the stations out to Hertford not covered by numbered zones, as well as Potters Bar and Radlett Zone 12, or Zone C, is station Zone 13, or Zone D, consists of the stations between zone 6 and Gatwick Airport Zone 14, or Zone E, is station Zone 15, or Zone F, was reserved for Elizabeth line stations out to , although it hasn't been used.