What i-Size is and why it appeared
i-Size is the common name for the European car seat standard UN R129, which is gradually replacing the older R44 that had been in force since the 1980s. The old standard classified seats by the child's weight and did not require a side-impact test, even though side collisions cause the most serious injuries to children. R129 was created to close these gaps and make seat selection less dependent on parental error.
Chosen by height, not weight
The key change in R129 is that a seat is matched by the child's height in centimetres, not by weight. This is more logical: weight says little about how the harness and headrest will sit on the body, whereas height directly determines the seating geometry. The shell of an i-Size seat always states a working range, for example "40–105 cm". Parents no longer have to guess which "group" their child belongs to — they simply fit by height. All modern VELANO car seats marked i-Size carry a clear height range on the label.
Mandatory side-impact test
R44 only tested a seat for frontal and rear impact. R129 added a mandatory side-impact crash test — the most dangerous scenario for a child. As a result, i-Size seats have reinforced side structures and deeper protective "wings" beside the head. This is not marketing but a structural requirement of certification.
Longer rearward-facing travel
R129 requires the child to travel rearward-facing until at least 15 months (not just to 9–13 kg, as R44 was often interpreted). An infant's neck cannot yet support the heavy head during hard braking, so the rearward-facing position cuts the risk of cervical injury many times over. In practice, doctors advise keeping a child rearward-facing for as long as the seat allows — often to 3–4 years.
i-Size and ISOFIX
The R129 standard is closely tied to ISOFIX mounting: most i-Size seats install this way, which removes installation errors. If you are not yet familiar with the system, read our guide on how to install ISOFIX. Belt-fitted R129 models also exist, but rigid mounting remains the priority.
R44: the effective phase-out
Production of new R44 seats in the EU has stopped: since September 2023 such models can no longer receive new certification, and shops are gradually selling off remaining stock. This does not mean your working R44/04 seat instantly becomes illegal — it may still be used while the certificate is valid and the service life is not exceeded. But if you are buying a seat today, there is no reason to choose the outdated standard.
| Parameter | R44/04 | R129 (i-Size) |
|---|---|---|
| Selection by | Weight | Height |
| Side impact | Not tested | Mandatory |
| Rearward-facing | To ~9–13 kg | Min. to 15 mo. |
| Mounting | Belt/ISOFIX | Mostly ISOFIX |
What this means for your choice
In short: for a new purchase, choose i-Size (R129). It is safer thanks to the side-impact test, easier to match because it ties to height, and keeps the child in the safest position for longer. Browse certified VELANO models, and once your child grows, also consider boosters built to the same standard.
