Stepup i-Size ISOFIX High-Back Booster – Midnight Black, 4-12 Years

A high-back booster with ISOFIX, for children who have outgrown a harnessed seat — roughly 4 to 12 years.

How a booster works

A booster does not have its own harness. It raises your child so the car's adult seat belt sits correctly: the lap belt low across the hips, the diagonal across the collarbone and chest.

That belt routing is the whole point. An adult belt on an unboosted child rides up onto the soft abdomen and across the neck, which in a collision causes the injuries boosters exist to prevent.

Why a high-back, not a booster cushion

The back gives side impact protection for the head and torso, and guides the diagonal belt to the right height. Backless cushions do neither. Under UK law backless boosters are only approved for children over 125cm and 22kg — a high-back is the right choice below that, and a better one above it.

ISOFIX or belted?

The ISOFIX version clips to your car's anchor points so the seat stays put when your child isn't in it — no sliding around, and no refitting each journey. The belted version at £34.99 is held by the seat belt alone and moves between cars more easily.

ISOFIX is worth the difference for a seat that lives in one car. The belted version suits grandparents, taxis and swapping between vehicles.

Check before you buy

Your car needs ISOFIX anchor points. Check your vehicle handbook, and check which positions are i-Size approved.

Features

• Approved to UN R129 (i-Size)
• Adjustable headrest that raises as your child grows
• Side impact protection
• Belt guides for correct diagonal routing

Important safety information

Read the manual before fitting. Check the belt routing every journey — the diagonal must cross the collarbone, never the neck, and the lap section must sit low across the hips, not the stomach.

Children must stay in a booster until they are 135cm tall or 12 years old, whichever comes first — that is UK law, and most children reach 12 before 135cm.

Replace after any collision, however minor. Never use a second-hand seat with unknown history.

Free fitting checks are available at many UK fire stations and retailers.