High-back booster seats

When your toddler reaches 18kg (usually around four years old), or is taller than 105cm, you'll need to swap to the next stage of child car seat – a Group 2/3 seat. This is what’s known as a high-back booster seat.

These child car seats are approved for use with children from 15-36kg, which is around three and a half to 12 years of age (around 36kg, or 135cm tall).

There's no need to swap to a Group 2/3 seat until your child has outgrown his or her toddler/Group 1 seat. This will happen when your child reaches around 18kg, or is too tall for the seat (i-Size-approved seats usually go up to 105cm). You'll be able to see this when your child's eyes are level with the top of the seat.

Some parents prefer to keep their child in a toddler seat for as long as possible because they're kept secured in the seat by a five-point harness, while a Group 2/3 seat uses the car's adult seatbelt to keep a child in place. Some may also be using an extended rear-facing seat, which will keep your child rearward facing until they're 105cm tall.

Our car seat experts recommend using the lowest group seat for as long as possible.

There are some seats available that let you extend the harness, or have other innovative ways of dealing with this issue.

Isofix and booster seats

Isofix connectors on a high-backed booster seat don’t work in the same way as they do for baby or toddler car seats. The connectors are used mainly to keep the seat stable and securely in place when it’s not in use, so it doesn’t fly forward and hit you if you have to brake suddenly or are involved in a crash and the kids aren't on board.

It’s the adult seatbelt in a Group 2/3 seat that helps to distribute the force of a crash away from a child’s body. Some seats in this category have Isofit connectors, rather than Isofix, They're similar but are more like soft latches, or hooks that attach to the anchor points in your car.

Find out more in our Isofix car seats guide.

Video: how to fit a high-back booster seat