The standard ticket is ticket "t+". It is valid for a multi-transfer journey within one and a half hours from the first validation. It can be used on the Métro, buses and trams, and in zone 1 of the RER. It allows unlimited transfers between the same mode of transport (i.e. Métro to Métro, bus to bus and tram to tram), between bus and tram, and between metro and RER zone 1. When transferring between the Metro and the RER, it is necessary to retain the ticket. The RER requires a valid ticket for entry and exit, even for a transfer. It costs €1.90 or ten (a "carnet") for €16.90 as of March 2020.