This service, operated by Beijing Municipal Red Cross, deploys 160 vehicles from a network of 64 bases around the capital. Vehicle positions are monitored by GPS, and under arrangement with China Mobile, the 999 service can trace callers with GPS-enabled phones to within a few dozen meters. The 999 service is confined to the Beijing municipality: outside Beijing the 120 number should always be used. Both the 120 and 999 services charge users at the time of transport. Fees are low by Western standards. The 120 service charges RMB 5 per km for its largest vehicle model, plus extra fees for treatments en route. The 999 service is usually a bit more expensive.