It is the United Nations regulation for the official approval of Child Restraint Systems. All child restraint systems used in countries in the European Union must meet the standards of this regulation.
This regulation specifies a range of tests and checks that validate the effectiveness of a child safety device in the event of an impact or accident, and verifies the stability of the product's characteristics by monitoring its production.
It also divides child restraint devices into five "mass groups" with different specifications:
a) group 0 for children weighing less than 10 kg;
b) group 0 + for children weighing less than 13 kg;
c) group I for children weighing between 9 kg and 18 kg;
d) group II for children weighing between 15 kg and 25 kg;
e) group III for children weighing between 22 kg and 36 kg.
Since 9 July, 2013, the ECE R44/04 Regulation has coexisted with the new ECE R129 (i-Size) Regulation.