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Size-i: the future of child seats

Size-i: the future of child seats


The new norm, Size-i has been developed to simplify your options when choosing a child seat, making them more universal and much simpler to use. It is a type of super ISOFIX. Just as ISOFIX begins with the letter i, so does this new regulation.
The principal innovations of Size-i are:

  • Ease of choice. As in the previous classifications of groups 0/0+/I/II/III (and their corresponding weight intervals) every seat will be graded with a size (height) and maximum weight up to which a child can use it in a similar way to children’s clothes sizes.
  • It includes a new lateral impact test to improve safety in this type of accident.
  • It guarantees the use of backward facing seats to at least 15 months of age. This will promote this much safer method for children to travel. At this point it is worth remembering that the MAPFRE FOUNDATION recommends that children, wherever possible, even if over 15 months, travel facing backwards (there are now seats on the market that allow this up to 3-4 years of age).
  • The new regulation gives maximum dimensions for the child seat and a minimum for the car seat so that the approved Size-i child seats are universal and can be used in any vehicle equipped with Size-i seats.
  • Improved crash testing using dummies that incorporate more advanced injury criteria.

One of the main advantages of the new regulation is better protection for the head and the neck in a head-on collision fostering the use of backward facing seats up to at least 15 months. This position can be 5 times safer than facing forward. It also provides better protection from a lateral collision and reduces the risk of incorrect installation. 

New regulations, new labeling

This is the new label to certify it conforms to the regulation ECE R 129.

Also, both the Size-i child seats and the seats in the latest cars will display the following label to indicate where they can be installed.


Once all cars are equipped with Size-i, which will eventually be the case, Size-i child seats will be suitable for every vehicle. Until then, their use in every vehicle is not guaranteed to be safe: for this reason every Size-i child seat includes a list of vehicles in which they can be installed safely even if they are not equipped with specific Size-i seats.

In Spain, legally, you may purchase and use Size-i child seats. Although at the moment there are not many available this will increase over time. As the new regulation does not replace the old one, seats approved according to ECE R44/04 can still be used without problem. The manufactures can opt for approval of their seats using either rating.

At the moment the new regulations ECE R 129, doesn’t cover every type of child seat. The first phase of these regulations only covers integrated seats (those with a harness to hold the child in the seat) with the ISOFIX system.

The second phase, now in development covers ISOFIX seats that are not integrated and support the child using the car seatbelts.
The third phase will work on the modifications needed to update the regulations ECE R44/04 for non-ISOFIX child seats (fixed to the vehicle using the seatbelt) and the regulations ECE 14 and ECE 16 (seatbelts and their anchoring to a vehicle) so that these seats conform to the criteria include in phase 1 and 2.

At the MAPFRE FOUNDATION we advise that you transport children as safely as possible always using a child seat suitable for their weight and height and always facing backwards wherever possible.

  (1) OFFICIAL STATE BULETIN, Num. 158 Monday 30th June 2014 section 1. Page 49879 published the order IET/1105/2014 from the MINISTRY OF INDUSTRY, ENERGY AND TOURISM of 26TH June updating the annexes I and II of the Royal Decree 2028/1986, of June 6th. Regarding the rules for applying regulations to certain vehicles, trailers, semi-trailers, motorbikes, mopeds and agricultural vehicles where ECE E129 is optional.

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