This part of ISO 22241 applies to diesel engine powered road vehicles using selective catalytic reduction (SCR) technology. It is primarily intended for use by passenger cars and light commercial vehicles including buses with a gross vehicle mass of not more than 3.5 t, but may also be used by vehicles with a gross vehicle mass of over 3,5 t. This part of ISO 22241 specifies the refilling interface for the NOx reduction agent AUS 32 in compliance with ISO 22241-1, which is needed to operate converters with selective catalytic reduction (SCR) exhaust treatment system. This part of ISO 22241 specifies the essential functional and geometric requirements of the refilling system in order to ensure compatibility between the on-board refilling system and the off-board refilling system. For light commercial vehicles and buses having a gross vehicle mass of not more than 3,5 t, the open refilling system specified in ISO 22241-4 can be used. NOTE Throughout this part of ISO 22241, the term “NOx reduction agent AUS 32” is abbreviated to “AUS 32”.