Review: Britax-Römer DUALFIX i-SIZE Extended Rear Facing Car Seat

Back in late 2017, I heard a few murmurings about a new, extended-rear facing, i-SIZE compliant car seat being launched by Britax Römer. This got me very – and probably more than I should be – excited because I’m a huge fan of their DUALFIX car seat, which I’ve reviewed here.

It turns out that my ‘sources’ were correct and an updated version of the DUALFIX was launched in December 2017 – called the DUALFIX i-SIZE. Unfortunately, I was unable to attend the actual launch event, but I luckily managed to get my hands on one of these highly-anticipated car seats after it was sent to me by Britax Römer for review.

Since then, it’s been sat in my car and amply tested by both myself and my 3.5-year old daughter. Below, you’ll find my full and detailed review of the car seat, however to give you the main headline, it’s a fantastic car seat and I have nothing but positives to say about it.

I loved the original DUALFIX, so it’s hardly surprising that I’m a big fan of the DUALFIX i-SIZE. In reality, the new car seat is similar to the predecessor, but they’ve made a few tweaks which have (somehow!) improved it. As the name suggests, the new DUALFIX i-SIZE is also i-SIZE compliant – something that all car seats will need to be in the future.

If you’re unfamiliar, i-SIZE is the new European Standard for child car seats which came out in 2013. Although this doesn’t make non-i-SIZE car seats redundant just yet, i-SIZE compliant seats meet additional criteria which give extra protection and safety for your kid.

For instance, i-SIZE car seats provide increased support for head and neck, better protection in case of frontal and side-impacts and a five-point harness in case the car rolls over. It also states that children must be rearward facing up to a minimum of 15 months and classifies seats by child’s height rather than weight.

So, with that in mind, let’s take a look at the new Britax Römer DUALFIX i-SIZE, which is both forward and rearward facing from birth to approx. four years old.

Product Description

The product is described as:

The Britax Römer DUALFIX i-SIZE car seat is the ideal first car seat for your baby, and is perfectly tailored to children aged from birth to four years. Integrated ISOFIX connectors help you to install your seat securely into your vehicle, while superior side impact protection uses energy absorbing technology to protect your child in the event of a side collision. It even rotates 360 degrees, so you can turn it towards the open car door to easily strap in your precious cargo and then use the seat in rearward-facing or forward-facing position. 

Britax Römer’s patented pivot link system greatly reduces the risk of head and neck injury by redirecting the force of impact downwards into the seat. The adjustable support leg gives this seat extra stability, minimising tilting and reducing forward movement forces exerted on your child if you are involved in an incident. 

The DUALFIX i-SIZE headrest is v-shaped to ensure optimal protection in the event of a side collision and, along with the harness, can be adjusted from the front of the seat to adapt to your child’s height. Soft, padded side wings act as a protective cocoon, while the 5-point harness with chest pads will leave your little one feeling safe and secure on every journey.

Review Britax-Roemer DUALFIX i-SIZE Extended Rear Facing Car Seat side view not installed

Product Experience

The Britax Römer UALFIX i-SIZE car seat arrived in a big box and was removed as one piece. The car seat is made up of an ISOFIX base with locking arms and adjustable leg, as well as the actual car seat where you place your child – this is attached to the base. There were also user instructions, ISOFIX insertion aids and the baby insert which is a removable section designed for use with babies up to 60cm.

The car seat was in Blue Marble – one of nine colours available. This features both a black and a blue denim-like material with peach detailing. Much like the original DUALFIX, the result is stylish, unique and very appealing. I did notice a couple of visual differences compared to the predecessor – for instance, the shock bar was more substantial and there definitely appeared to be more bulk (and therefore protection) around the sides thanks to being i-SIZE compliant.

The first thing to note is that the DUALFIX i-SIZE isn’t an infant carrier. It is designed to be installed and stay in the vehicle, rather than separating the car seat from the base and fitting it onto a travel system. This is fine for us as we use it with a 3.5 year old, however it would mean less flexibility if we were to use it for our newborn son (we instead have a Britax BABY-SAFE i-SIZE). We’ll often take his car seat out of the car whilst he’s in it, which we’d not be able to do with this one. This is a preference thing though.

Installation was very simple – you place the DUALFIX i-SIZE in the car and adjust the shock bar so that it matches the angle of your back seat. There’s then a fabric loop to pull, which extends the ISOFIX locking arms and allows you to line these up with the ISOFIX points in the car. This is where you use the ISOFIX insertion aids if you don’t have them on your car as standard (we do).

Review Britax-Roemer DUALFIX i-SIZE Extended Rear Facing Car Seat ISOFIX locking arms on ISOFIX point

You’re then able to push the car seat towards the back seat of the car, which engages and locks the arms with the ISOFIX points – an audible click and a green indicator on each arm shows that they are installed properly.

The final part of installation is the support leg. This is pulled away from the car seat, then adjusted to rest firmly on the floor of the vehicle. Again, you’ll be able to hear it click into place and see that it is correctly installed through the indicator which has gone from red to green.

Review Britax-Roemer DUALFIX i-SIZE Extended Rear Facing Car Seat side view installed properly

Installation of the DUALFIX i-SIZE was very similar to installation of the predecessor – the only difference was adjusting the shock bar which I think is a nice addition as it ensures even more stability as it lies flush with the back seat. It took no longer than one minutes to install – partly because it’s easy and partly because I’m used to the DUALFIX. To take the car seat out, you just need to detach the ISOFIX locking arms with buttons on the side – the car seat can then be lifted out and fitted into another vehicle.

It’s worthwhile noting that the car seat is bulky and quite heavy. You need to have the car doors fully opened and a fair bit of space to manoeuvre it into the car. At 15kg, the DUALFIX i-SIZE is actually slightly heavier than the original DUALFIX too. I’d have liked to have seen weight taken off the car seat rather than added, but I guess the extra i-SIZE protection has done the opposite. The weight isn’t unmanageable, but you do get a bit of a sweat on!

Review Britax-Roemer DUALFIX i-SIZE Extended Rear Facing Car Seat side installed in car

The DUALFIX i-SIZE can be used with kids from 40cm to 105cm – which is approximately birth to four years old – in both forward and rearward facing modes. This means that you could buy this car seat at birth, then it would grow with them until they reach 105cm tall – therefore negating the need to buy another car seat when they hit 15 months (assuming you just bought a 0+ group car seat).

With this car seat, the baby would be rearward facing until 76cm / 15 months old, then you’d have the option of switching them to forward facing or alternatively keeping them rear facing. The latter is what we’ve done with L – evidence shows that extended rearward facing is much safer, so we’ve always kept her rear facing and will do until she grows out of this at 105cm. She’s currently around 95cm and has plenty of leg room in both versions of the DUALFIX.

Review Britax-Roemer DUALFIX i-SIZE Extended Rear Facing Car Seat in car toddler rear facing

One of may favourite things about the DUALFIX i-SIZE – and it’s predecessor – is the ability to rotate the car seat a full 360 degrees. This makes it easy to move from rear facing to forward facing if you wanted to, but also means getting into the seat is a doddle. Buy turning the seat 90 degrees to face the open door, you’re able to fasten your kid into the seat from a much easier position.

As they get older, it also allows them to climb into the seat themselves – a lifesaver when you’re dealing with multiple kids. To turn the seat, there’s a grey ‘rotation button’ on the side that you push – this then allows you to swivel the seat in the direction you wish. Once your kid is in the car, you then rotate the seat back and it clicks and locks into place. Interestingly, the rotation button has been moved to the side, which feels a more natural position (on the original DUALFIX, it’s at the front).

Review Britax-Roemer DUALFIX i-SIZE Extended Rear Facing Car Seat in car rotated outwards

Securing your kid into the car seat is simple too. You put them into the car seat, pull the straps over their shoulders, push the two tongues of the buckle together, then securely place this into the buckle harness. You then pull the grey adjustment strap which dangles down to tighten the harness around your child. Unlike other car seats we’ve used, I have 100% confidence in the fact that L is securely fastened and isn’t able to get her arms out. Everything also feels very premium, padded and soft.

Review Britax-Roemer DUALFIX i-SIZE Extended Rear Facing Car Seat 5 point harness

To take your child out of the car seat, you need to do the opposite. Press the red button on the buckle harness to release the 5-point harness. Then, loosen the shoulder straps by pressing in the silver adjustment button (located by the adjustment strap) whilst pulling on the straps.

Depending on the size of your kid dictates whether you need to adjust the headrest. As we’re using the seat for an approx. 95cm preschooler, we moved the headrest up so that the shoulder straps were in line with her shoulders. This is done with a release button on the headrest. Again, easy and fast.

Review Britax-Roemer DUALFIX i-SIZE Extended Rear Facing Car Seat shoulder pad

The final thing to mention about the DUALFIX i-SIZE is that it comes with six recline options in either forward or reward facing modes. Pulling the adjustment handle under the front of the seat allows you to slide the car seat up or down until you find the correct recline position of choice.

Now, this is where it’s interesting – for me at least – because I’ve noticed differences between the DUALFIX i-SIZE and original DUALFIX here. In essence, the latest model has been simplified – and for the better in my view. Firstly, the car seat will rotate in ANY recline position – something that the DUALFIX couldn’t do as it only rotated in the highest or lowest recline.

Secondly, there is now no weight restriction, meaning that L can lie in the most reclined position – again, something she couldn’t do in the DUALFIX because she was in the ‘9kg to 18kg’ setting rather than ‘0kg to 13kg’. What this has done however, is remove the inbuilt safety feature of not allowing a ‘0kg to 13kg’ child to be forward facing.

Both of these points were little niggles I had with the DUALFIX (and had mentioned in my previous review), so I’m very happy that they’ve been updated for the DUALFIX i-SIZE. Maybe I should go into car seat design?!

Review Britax-Roemer DUALFIX i-SIZE Extended Rear Facing Car Seat side view SICT

All in all, I love this car seat and can’t fault it at all. I was very impressed with the original DUALFIX and had very few negatives comments. It’s therefore no surprise that I’m struggling to find anything bad to say about an updated and improved version – particularly as it now i-SIZE compliant,which means extra protection. It is – without doubt – the best car seat we’ve owned.


The Britax Römer DUALFIX i-SIZE costs £430 and can be bought from retailers including Mothercare and Halfords. At this price, it can hardly be considered cheap – however, what you’re getting is one of the top extended rear facing, i-SIZE compliant car seats on the market. Also, remember that this will last you for four years, which arguably means it’d be a similar amount of money when compared to having to buy two car seats as your child grows.

N.B. As another option, the original DUALFIX is still being sold and is now heavily discounted – as low as £259 on Amazon. Considering non-i-SIZE car seats can still be used, and how awesome the original version is, you could consider going for the predecessor over the new model.


The Britax Römer DUALFIX i-SIZE is a fantastic car seat and I have nothing but positives to say. It is a beautifully designed and built bit of kit, whilst the Blue Marble colour scheme really makes it stand out. It is suitable from birth to four (40cm to 105cm), is both forward facing and rearward facing (including extended rear facing to 4 years old), has 360 degrees rotation and is i-SIZE compliant.

I loved – and still love – the original DUALFIX. However, what Britax has done here is take an already exceptional product and somehow make it even better. Apart from the changes to make it i-SIZE compliant, there’s not actually any other major changes. Instead, they’ve made little changes- the location of the rotate button, the ability to rotate in any reclined position, removing the weight restriction on recline positions – which do improve the car seat.

Sure, it’s a little heavier than I’d like and at £430 it’s hardly cheap, but with the Britax Römer DUALFIX i-SIZE, you’re getting one of the best extended rear facing, i-SIZE compliant car seats on the market. It gets my seal of approval and I’d have no qualms in recommending it to others. Good work Britax Römer!

The DADventurer Star Rating

5 out of 5 stars


Disclosure: The DUALFIX i-SIZE car seat was sent to me by Britax Römer with the purpose of writing an honest review in exchange for the product.

Disclosure: This post includes an affiliate link(s).