As used for gas, a bilateral agreement between a user of the national transmission system (NTS) and National Gas Transmission (NGT) to take gas off the NTS, or a user of a gas distribution network (GDN) and the GDN operator to take gas off the GDN. The operator of a gas-fired power station, or a GDN operator, that is connected to the NTS will have a NExA with NGT. The NExA will set out the gas pressure associated with the exit point, gas quality requirement, the ramp rate, and notice periods for increases in offtake rates. For more information on the NTS and GDNs, see Practice note, Downstream gas industry: overview.