This is a Twin pack of disposable breathalysers (2 x breathalyzer tubes and 2 x reusable blow bags manufactured by Contralco) - under French law you MUST always have an 'unused' device in your car. If you use one tube to test yourself, or break or lose one (they are small !) and do not have a 'spare', then you will be illegal and liable to a fine
From Spring 2012, all vehicles driving in France will be required to have a breathalyser on board. In order to comply it is ESSENTIAL that the breathalyzer complies with French Law and is NF (French Laboratory) approved.