i-Size explained

What is i-Size?

i-Size is the name for car seats approved under the European regulation UN R129, which replaces the older R44. An approved seat has a label with ‘R129’ and the heights it is suitable for.

R129 also tests for side impacts, which R44 did not require. Which seat fits your car is shown in the vehicle list the seat’s manufacturer publishes.

Height instead of weight

Under R44, parents chose a seat by weight group, such as 0+ or 1. Under R129 the manufacturer states the child’s height, for example 40–87 cm. That is easier to measure and fits better with how children grow.

On LeBaby every car seat lists the height and, where the manufacturer gives it, the maximum weight. A seat that grows with your child and covers several classes appears in each of them.

Rear-facing for longer

R129 requires a child to ride rear-facing until at least 15 months. Many seats can be used rear-facing for longer; the height and weight up to which that works are in the specifications.

Isofix and the support leg

Many i-Size seats or their bases click onto the car with Isofix, often with a support leg or a top tether. Whether that works in your car is in the car’s manual and in the manufacturer’s vehicle list.

And an older R44 seat?

Since 1 September 2024, new R44 seats may no longer be sold in the EU. An R44 seat you already own may still be used in the Netherlands and Belgium. Do check that it is undamaged and has never been in an accident.