Directive 2004/22/EC on Measuring Instruments (MID) was adopted by the European Parliament and Council on 31 March 2004, for application by EU Member States from 30 October 2006. The Directive takes precedence over national regulations in each Member State. It covers ten categories of measuring instruments and is designed to harmonize the requirements for new measuring instruments placed on the market or put into use in Europe by eliminating the regulatory differences at national level which hinder trade. This new-approach Directive allows manufacturers to choose between various conformity assessment procedures for their instruments. It reinforces European standards and OIML recommendations, and introduces the notion of presumption of conformity to essential requirements. Certificates of conformity to the MID Directive are valid throughout Europe. It will therefore be easier for manufacturers to market their controlled measuring instruments.