"IDBI FASTag is a thick paper based tag / device that use Radio Frequency Identification (RFID) technology for making toll payments directly from the Prepaid Wallet Savings or Current account linked to it. It is to be affixed on the windscreen of your vehicle which enables you to drive through toll plazas without stopping for cash payments as toll charges.

The Government of India has mandated that all new vehicles being sold with effect from 1st December 2017 are to be affixed with FASTag. The FASTag Partner App will facilitate more than 6000 dealers in the country to access a single platform and activate the FASTag at the time of delivery of vehicle.
IDBI FASTag has been made mandatory on 600 + National Highways toll plazas (check for the list here) and is acceptable across over and selected 54+ State highways toll plazas.

From 15th December 2019 all lanes at National Highway toll plaza will be declared as dedicated FASTag Lane except for one Hybrid lane. Non -FASTag users will be charged double the fee if they pass through FASTag lanes."