• Black high-back car seat with padded headrest, side wings, and green adjustment pads
  • Black high-back booster seat with green armrest accents installed in rear passenger seat
  • Child in black high-back booster car seat with green armrest and shoulder belt
  • For Your Little One Stepup I-Size Isofix 2/3 Car Seat Booster Seat - Midnight Black (4-12 Years)
  • Midnight black car booster seat with padded headrest and turquoise adjustment accents
  • Black car booster seat reclined side view with turquoise side arm and base hardware
  • Black car booster seat front view with logo headrest pads and turquoise lower anchors
  • Black car booster seat with green headrest guides and ISOFIX base, side view
  • Black car booster seat back view with padded headrest and turquoise anchor points
  • Black car booster seat front three-quarter view with headrest and turquoise arm rests
  • Black car booster seat side profile with wide headrest and turquoise adjustment handle
  • Black car booster seat side view with instruction label and turquoise belt guide
  • Midnight black car booster seat front view with quilted seat cover and turquoise accents
  • Black car booster seat side view with quilted seat pad and turquoise adjustment handles
  • Black car booster seat rear side view with adjustment frame and turquoise handle
For Your Little One

For Your Little One Stepup I-Size Isofix 2/3 Car Seat Booster Seat - Midnight Black (4-12 Years)

Good to know i-Size ISOFIX Group 2/3 | Secure Click-In Fit | 4–12 Years
£49.99 £79.99 Save 37% In stock

VAT included. Shipping calculated at checkout.

FREE Delivery On orders over £49.99
Order before 2.30pm For same day dispatch
Buy with confidence Warranty included
Secure checkout
American Express Apple Pay Diners Club Discover Google Pay Klarna Maestro Mastercard PayPal Shop Pay Union Pay Visa
Klarna
Pay in 3 Interest-free payments
Clearpay
Pay in 4 Interest-free payments
Suitable for children 100–150cm in height (approx. 4–12 years)

Group 2: 15–25kg (approx. 4–6 years) — Forward-facing
Group 3: 22–36kg (approx. 6–12 years) — High-back booster mode

Installation: ISOFIX — check your vehicle is ISOFIX compatible before purchase
Always check your child's height against the seat's headrest guide before use
1x Stepup i-Size ISOFIX Car Seat (Midnight Black)
1x User Manual
✔ i-Size (R129) Certified — Exceeds current EU safety regulations
✔ Rigid ISOFIX connection — click-in installation eliminates fitting errors
✔ Fits children 100–150cm (approx. 4–12 years) — Group 2 & 3
✔ Deep padded side-impact protection wings
✔ One-hand adjustable headrest — multiple height positions, no tools needed
✔ Premium breathable padding for all-day comfort
✔ Removable, machine-washable seat cover

Designed to keep your child safe and comfortable from 100 cm to 150 cm (approximately 4 to 12 years), the Stepup i-Size ISOFIX car seat is the last car seat you'll ever need to buy for this stage. Built to the latest UN R129 i-Size safety standard, it delivers superior side-impact protection and a rock-solid ISOFIX connection every single time.

Why Parents Love It

  • i-Size Certified (UN R129) — Exceeds current EU safety regulations for enhanced protection
  • ISOFIX Installation — Rigid, click-in connection eliminates installation errors for total peace of mind
  • Fits 100–150 cm (approx. 4–12 years) — Grows with your child through Group 2 and Group 3 stages
  • Side-Impact Protection — Deep, padded side wings absorb and deflect impact energy away from your child
  • One-Hand Adjustable Headrest — Multiple height positions adapt quickly as your child grows, no tools required
  • Removable, Machine-Washable Cover — Easy to keep fresh and clean
  • Midnight Black Finish — Sleek, premium look that suits any car interior

Safety You Can Trust

The Stepup i-Size meets the stringent UN R129 regulation, which requires extended side-impact testing and a minimum height requirement — giving your child significantly more protection than older Group 2/3 seats. The rigid ISOFIX connection anchors the seat directly to your car's chassis, removing the risk of incorrect belt-only installation.

Comfort for Every Journey

Thick, breathable padding and a one-hand adjustable headrest with multiple height positions mean your child can settle in comfortably whether it's the school run or a long motorway trip.

Specifications

  • Safety Standard: UN R129 (i-Size)
  • Child Height: 100–150 cm
  • Approx. Age: 4–12 years
  • Installation: ISOFIX
  • Facing Direction: Forward-facing
  • Cover: Removable & machine washable
  • Colour: Midnight Black
Black high-back car seat with padded headrest, side wings, and green adjustment pads
For Your Little One Stepup I-Size Isofix 2/3 Car Seat Booster Seat - Midnight Black (4-12 Years)
£49.99
£49.99 -37%
£79.99
Supporting families since 2011
Trusted by families across the UK
Read our customer reviews on Trustpilot

Trusted by UK families

A safe and reliable place to shop for little ones

Free UK Delivery

On UK mainland orders over £49.99

Same-Day Dispatch

Order by 2.30pm for same-day dispatch

Easy Returns

Simple returns for extra peace of mind

Why you'll love it

Designed around family life

Discover the features, thoughtful details and benefits designed to make life with little ones easier.

i-Size Safety That Exceeds the Standard
01

i-Size Safety That Exceeds the Standard

The Stepup i-Size is certified to UN R129 — the latest and most rigorous car seat safety regulation in Europe. Unlike older Group 2/3 seats, i-Size requires mandatory side-impact testing, meaning your child is protected from impacts that traditional standards don't even test for. Paired with rigid ISOFIX connectors, the seat locks directly into your car's chassis for a secure, error-free fit every time you travel.
For Your Little One Stepup I-Size Isofix 2/3 Car Seat Booster Seat - Midnight Black (4-12 Years)
02

Grows With Your Child From 4 to 12 Years

Covering 100 cm to 150 cm in height, the Stepup takes your child through both Group 2 and Group 3 stages in a single seat — no mid-stage upgrades needed. The one-hand adjustable headrest moves in seconds to match your child's growing height, while the deep padded side wings reposition automatically to keep protection exactly where it's needed at every stage.
Comfort Built for Real Family Life
03

Comfort Built for Real Family Life

The breathable, premium-padded cover keeps them cool in summer and cosy in winter — and when it needs a refresh, simply remove it and pop it in the washing machine at 30°C. The Midnight Black finish looks sharp in any car interior and hides everyday wear beautifully.
Designed for family life Comfort & practicality Made for everyday adventures

Customers praised this I-Size ISOFIX booster seat for being "sturdy," "comfortable," and "easy to install." Many noted excellent value for price and strong build quality. Children found it comfortable on long journeys with good side support. One customer mentioned difficulty connecting the seat belt due to the wide base.

  • Really impressed with how sturdy this feels. My child is comfortable even on longer journeys.
  • Easy to get fitted with the ISOFIX and it sits nicely in the car.
  • A lovely booster seat and much nicer than I expected for the price.
  • 5 stars: 56 (98%)
  • 4 stars: 1 (2%)
  • 3 stars: 0 (0%)
  • 2 stars: 0 (0%)
  • 1 star: 0 (0%)
R
Rollerdave
This is a comfortable seat or booster for my

This is a comfortable seat or booster for my grandson who simply has outgrown his initial car seat.
Delivery was quick and it appears well made. My only issue and this actually may be a common problem is that it’s incredibly difficult to connect the seat belt because the base is fairly wide. I’m not sure if this is a common problem with booster seats but it’s a Ford Kuga which is a reasonably sized car so I didn’t anticipate this problem.

E
Emma T.
Fast delivery

Ordered in the afternoon and it arrived very quickly. Well packed and the seat was exactly as described.

S
Sophie M.
Great quality

Really impressed with how sturdy this feels. My child is comfortable even on longer journeys.

O
Olivia R.
Simple to install

Used it on a long trip already and there were no complaints. Comfortable seat and easy to buckle in.

A
Amelia K.
Solid and comfortable

Easy to get fitted with the ISOFIX and it sits nicely in the car. Feels much more secure than our old booster.

E
Emily J.
Great booster seat

A lovely booster seat and much nicer than I expected for the price. Feels supportive and well made.

C
Charlotte B.
Excellent service

I had a question about fitting before using it and customer support were really helpful. They replied quickly and sorted everything for me.

J
Jessica H.
Simple to install

Bought this for my 4 year old and it has been great so far. Comfortable, supportive and easy to use every day.

L
Lucy P.
Solid and comfortable

Bought this for the grandparents car and it was really easy to fit. No fuss and feels nice and secure.

H
Hannah W.
Fast delivery

Really impressed with the delivery. It arrived sooner than expected and was well packaged with everything in perfect condition.

G
Grace D.
Great quality

The seat feels really well made and the padding is comfortable. My little one is very happy sitting in it.

M
Megan S.
Simple to install

My son says this is much comfier than his previous seat. It also looks really smart in the car.

C
Chloe A.
Solid and comfortable

Nice sturdy booster with good support around the sides. My daughter settled into it straight away.

L
Lauren C.
Great booster seat

Looks smart in Midnight Black and feels solid once fitted. Really happy with the quality for the price.

R
Rebecca N.
Great quality

Good quality seat that feels strong without being too bulky. Very easy for us to use day to day.

S
Sarah L.
Simple to install

We have been using this every day and are really pleased with it. Simple, comfortable and feels safe and secure.

K
Katie F.
Helpful customer service

Contacted support with a question about the ISOFIX fitting and they were brilliant. Clear advice and resolved my query straight away.

A
Amy G.
Great booster seat

Really happy with this. The head support is good and it feels like it will last us for years.

L
Laura V.
Quick delivery

Fast delivery and no issues at all. Got it fitted the same day and we are really pleased with the seat.

R
Rachel P.
Simple to install

Very straightforward to install and feels secure with the ISOFIX. The seat belt sits nicely too.

C
Claire M.
Solid and comfortable

Exactly what we were looking for as our child moved into the next stage seat. Comfortable and secure.

N
Natalie J.
Great booster seat

Really pleased with this booster seat. It feels sturdy and secure and my child says it is very comfortable.

B
Beth R.
Great quality

Really impressed with how sturdy this feels. My child is comfortable even on longer journeys.

G
Gemma H.
Simple to install

Used it on a long trip already and there were no complaints. Comfortable seat and easy to buckle in.

V
Victoria S.
Solid and comfortable

Easy to get fitted with the ISOFIX and it sits nicely in the car. Feels much more secure than our old booster.

J
Jade K.
Great booster seat

A lovely booster seat and much nicer than I expected for the price. Feels supportive and well made.

N
Nicole B.
Support were brilliant

Had a small query after delivery and the customer service team were very helpful. Quick response and everything was sorted without any hassle.

E
Ellie D.
Simple to install

Bought this for my 4 year old and it has been great so far. Comfortable, supportive and easy to use every day.

Z
Zoe W.
Arrived quickly

The seat arrived quickly and was packed really well. Looks great and was straightforward to get installed.

E
Emma T.
Great booster seat

Fitting was easier than expected and once clipped into the ISOFIX points it felt really secure.

S
Sophie M.
Great quality

The seat feels really well made and the padding is comfortable. My little one is very happy sitting in it.

Just for you

You might also like

A few more products you may love, selected to complement what you're currently viewing.

We don't have any recommendations for this product yet.
You've been browsing

Recently viewed

Pick up where you left off and revisit products you've recently viewed.

Your recently viewed products will appear here.