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Britax Römer Dualfix i-Size review

If you won’t be switching your car seat between cars, then this extended rear-facing seat is a great buy. Rigorously tested and premium in quality, the Britax Römer Dualfix i-Size offers good longevity and allows you to keep your child rear-facing for as long as possible.

By Mumsnet HQ | Last updated Dec 4, 2023

Britax Romer car seat

At a glance

  • Age range: Birth to 4 years (weight 0-18kg, height 40-105cm); rearward-facing from 40-105cm; forward-facing from 76-105cm

  • Safety credentials: ECE R-129; Stiftung Warentest – 2,1; ADAC 2.1; ÖAMTC – good; optimised side impact protection; pivot-linked ISOFIX system

  • Fixing system: ISOFIX

  • Dimensions: 48 × 44 × 74cm

  • Weight: 15kg

  • RRP: £430, but widely available for less than £400

  • Guarantee: Two years


  • Innovative safety features

  • Newborn insert to make sure your baby is safe and comfortable from birth onwards

  • 360-degree rotation

  • 12 recline positions

  • Lots of extra accessories to buy online including a mirror, summer seat cover, kick pad – all very tempting!

  • Can be used from birth right up to four years – that’s 200 weeks and 1500 days of use


  • Very big seat that takes up a lot of room

  • Tricky to fit initially – and the video isn’t that helpful either

  • Can’t be used as part of a travel system

  • The price

Key features

  • Has undergone rigorous testing

  • Height-adjustable support leg

  • Deep, protective side wings to absorb force from a side impact

  • V-shaped headrest – again, provides protection in the event of a side collision (and it’s comfy too)

  • Neoprene chest pads

  • Five-point harness

  • Washable, quick-remove cover – a real bonus for busy parents

  • Adjustable rebound bar to give your child more leg space

Britax romer

How safe is the Britax Römer Dualfix i-Size?

The Britax Römer Dualfix i-Size, an updated version of the ever-popular Dualfix, has some fantastic safety credentials. Everything is designed to provide safety, security and comfort for your baby – and Britax Römer claims that its internal standards are higher than the tests laid out by the R129 regulation.

What are the safety features?

The car seat’s safety features include optimised Side Impact Cushion Technology (SICT), which absorbs the force of any side impact and is implemented by a special steel element inside the seat. In a side impact, the bar acts like a protective shell which, together with the softly padded side wings, forms a protective cocoon around your child. As the steel bar deforms, it absorbs energy and guides forces into the inner part of the seat, away from your child.

The side wings act as a cocoon, the headrest controls the movement of your baby’s head, the rebound bar and support leg give extra support to the seat, and the ISOFIX system reduces the force of an impact, whether it's from the front, from the side or from the back.

The five point-harness also keeps baby safe and secure (there's no chance of them wriggling out either) and the extra cushioning and chest pads ensure a snug fit across your child's chest, shoulder and pelvis.

As should be the case in a baby car seat, there’s no chance of anything coming loose that could be a choking hazard. This seat is durable, sturdy and, once installed, doesn’t wobble giving you all the assurance you need. And there’s nothing here that could irritate baby’s delicate skin either.

How does it grow with my child?

It’s a fact of life that kids grow fast, and you’ll only need to make small adjustments to the seat to keep up with them. With a simple push of a button on the side of the seat, you can move the headrest and harness. Another button on the seat adjusts the leg supports and rebound bar when your child gets a bit taller.

If you’ve got a Peter Crouch in the making, you’ll be grateful for the rebound bar which adjusts eight degrees and gives extra space when rear-facing.

A big USP of the Dualfix i-Size is that it features six different forward-facing positions and six rearward-facing positions, including a flat recline position for newborns. This is helpful if you think you’ll be doing a lot of driving with a newborn. You might also find that your baby settles better in one of the positions or that they seem to sleep for longer in another. Whatever works, right?

This seat, however, is designed for use from birth to around four years and is recommended for use in the rear-facing position for all of this time. If your child can’t wait to be front-facing though, you can turn the seat around once they’re taller than 76cm. This is likely to be when they’re around 15 months. Once your child reaches 105cm they’ll have outgrown this car seat and you’ll need to move them into a different model.

How does it look?

The Dualfix i-Size looks and feels expensive. It is solid and well-made and the outer shell is strong and sturdy. Add to this the wings on either side and your baby will look completely snug and safe.

Britax Römer has stuck with its classic look for the updated Dualfix. The Dualfix i-Size comes with a black shell, rather than white, but the same colour options and sleek hallmarks are all there.

Its cover is 100% polyester and available in no less than 10 colours, so there's bound to be one that you like (although some of the lighter shades may only be for the brave). Our tester, Sam's, seat was blue marble and the fabric felt very luxurious. The seat is also designed to appeal to your child as they grow – nothing twee or babyish here.

There are lots of extra touches to ensure a child is comfortable while travelling – 12 recline positions (including an ergonomic lie-flat position), a newborn insert, soft padded side wings, a V-shaped headrest and comfortable neoprene chest pads, which will take a lot of the stress off parents. So, while it’s pricey, this seat has a great deal to recommend it.

Getting going

Everything you need is included in the box. Firstly, the Dualfix i-Size needs to be attached to the ISOFIX anchorage points in your car – the ISOFIX base is built into the seat, as is the adjustable foot prop for maximum stability, which will make the Dualfix i-Size a semi-permanent feature in the back of your car.

It did take some huffing and puffing for Sam to install the seat the first time round as it took her ages to figure out how to pull out the ISOFIX fittings at the front of the chair.

There’s a pull-out strip of fabric that you are supposed to pull to release the ISOFIX fittings and, despite her yanking on this several times, nothing happened. In desperation, she had to fumble around inside the mechanism and managed to wrestle the ISOFIX fittings out to install the car seat into the car. It really shouldn’t be that difficult.

While the support leg is easy to adjust out of the car, it's harder once the car seat is inside – it was a bit stiff and it took some elbow grease to fix into place.

Is it easy to fix into place?

However, once the leg is sorted and the ISOFIX jostled into place, fitting the seat is easy. It slips right into the ISOFIX anchor points and the rebound bar tilts slightly to adapt to the recline of your seat. Thankfully, if you keep the seat in the car, you should really only ever need to set it up once.

You’ll know you’ve fitted the seat correctly when both ISOFIX indicators are green. Use the two buttons on the side of the leg to release and pull it down. When it’s locked in the correct position, the indicator will be green.

Once the seat is safely installed, you can leave it in place. The seat rotates, so you can turn it towards you and, once baby is in correctly, you can simply spin it into place – the red indicator at the bottom will turn black once it’s locked.

Because this seat is best used in only one car, you can take your time to ensure that it’s installed properly. And the indicators give you the confidence that you’re doing this right.

The paper instructions are really easy to follow and understand. When it comes to video tutorials, the first video you’re directed to on the website feels a lot more like advertising than an installation guide so you'll need to watch the second video.

There’s a whole support section online with FAQs, warranty details, product support information and contact details too.

Britax romer

What's it like to use day-to-day?

Once the seat is installed, getting your baby in and out is really easy. It’s a high seat so there’s minimal bending over and the straps are also easy to secure, tighten and release. Once your baby is in the seat, you pull on the strap at the bottom until it’s all secure. Very quick and easy to do even if you’re in a rush.

The best bit, though, according to our tester, is the 360-degree swivel function. The button to spin the seat is easy to reach and cleverly attached to the base of the seat, which means you can rotate it effortlessly to put your baby in (before moving it back into the correct position) and take them out without hassle – a huge plus when it comes to busy family life and less of a back-breaking task.

For older kids wanting some independence, they’ll be able to clamber in by themselves.

The overall design means this seat will continue to appeal to your child as they grow and the 12 recline positions means that your child will be comfy at all times.

Changing the seat's configuration to suit a growing child is also very simple. The newborn insert can simply be removed when no longer needed, the headrest is adjustable – simply pull it up to the required height – and the straps can easily be adjusted.

There’s nothing to distract the driver – the seat doesn’t obstruct the driver’s view, despite being on the large side, and Sam felt confident that her baby was safe.

This is a big seat, though, and, depending on your car, you’d probably find it difficult to have more than two infant or child car seats in the back when using the Dualfix i-Size. If you are using two of these seats at any one time, they are so large that, if you rotate one seat to get one baby out, you need to put the seat back into position before you can rotate the other seat. Not a massive issue though.

What about longer journeys?

Sam felt that this seat was too big to take on a holiday that involves flying – it would have to go in the hold, and would be a pain to transport. But for long car journeys, this seat is great – her baby was the happiest she’s ever been in a car seat, which means Sam was happy too.

For the school run or a trip to the shops, this seat is easy to use, and for those longer trips you can be confident your baby is safe and comfortable.

The only real issue with a seat like this is that it's fairly heavy at 15kg and isn't designed to be used as a carrier so will likely stay in your car for the foreseeable future. This means that you will need to take your baby out of the seat at the end of a trip.

If you'd like to use this car seat in multiple cars, prepare yourself for a bit of a workout. If not, and you need to be able safely transport a sleeping baby into the house while they're still in their car seat, smaller models like the Maxi-Cosi Rock and the Mothercare Ziba may be more up your street.

How easy is it to clean?

The machine-washable seat cover is quick and easy to remove when inevitable spillages occur – you can even leave the harness in place while you do this – and the soft neoprene chest pads can also be whipped out and wiped clean.

This was much less fiddly than a lot of other seats we tested like the BeSafe iZi Go, where you’d need to set aside a good 10 minutes to get everything off and then on again, or the Cybex Gold Aton M with hard-to-reach poppers that made it really frustrating to remove the covers.

As a whole, the Dualfix i-Size performed well in our cleaning test. Both milk and juice came out easily with a damp cloth and soapy water, and on the first try too. Given that the seat we tested was light in colour (blue marble), this was really impressive.

For a deeper clean, the cover is machine-washable, which will be a big plus for a lot of parents.

Britax romer put in

What about value for money?

The Britax Römer Dualfix i-Size certainly isn’t cheap, but you can use it right up until your child is four (as long as it isn’t involved in any accidents) and it can be tested to the highest of safety standards.

On balance, we feel it’s worth the money, especially as you can find it from reputable stores at a lot less than the RRP.

Final verdict?

If you’re looking for a really top notch seat, which is long-lasting and rigorously tested, then the Britax Römer Dualfix i-Size is a sensible buy.

You can be assured that your baby is safe and comfortable at all times, and you won’t have to worry about buying another seat until they’re off to school too.

About Mumsnet Reviews

All Mumsnet product reviews are written by real parents after weeks of research and testing – this includes recommendations from the Mumsnet Talk boards. We work hard to provide honest and independent advice you can trust. Sometimes, we earn revenue through affiliate (click-to-buy) links in our articles. However, we never allow this to influence our coverage.

All prices correct at time of publication

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