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Cybex Sirona Gi i-Size review: our verdict on the new 360 extended rear-facing car seat

New for 2023, the Sirona Gi i-Size is the latest 360 spin car seat from popular car seat and pushchair brand, Cybex. After three months of in-depth testing with parent and MNHQ editor, Laura, here’s our verdict on the newest addition to the popular Sirona line. 

By Laura Westerman | Last updated Oct 25, 2023

Cybex Sirona Gi i-Size car seat

Overall star rating: 4.5/5

RRP: £300-£325 | Buy now from Amazon

Key specs

Age range: From birth with newborn inlay; otherwise from 3 months to 4 years (or 20kg); 61 to 105cm (from 40cm with newborn inlay) | Safety credentials: i-Size (R129), integrated Linear Side-impact Protection (LSP), energy reduction technology for safer forward-facing, travel rear-facing for longer | Fixing system: ISOFIX | Dimensions: 71 x 44 x 75cm | Weight: 13kg | Warranty: 3 years

What we like

  • 360-degree rotation for easy boarding

  • Integrated air ventilation and mesh fabrics

  • Easy recline with five different settings

  • Fast one-click installation with indicators to ensure correct fitting

  • Padded seat

  • Good value for money

What we don’t like

  • 360-degree rotation mechanism sometimes quite stiff

  • Limits how much the adult seat in front can move or recline

  • Unsuitable for babies under 3 months unless newborn insert bought separately

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Our verdict on the Cybex Sirona Gi i-Size

  • Installation: 4.5/5

  • Safety: 5/5

  • Ease of use: 4/5 

  • Design: 4.5/5

  • Ease of cleaning: 4/5

  • Value for money: 4.5/5

With excellent safety credentials, high-quality fabrics and an integrated ISOFIX base, the Cybex Sirona Gi i-Size car seat is worth investing in.

Suitable from birth with the newborn insert or from three months old without, this extended rear-facing car seat will last until your child is around four years old or 105cm in height, whichever comes first.

You can switch to forward-facing with this car seat from 15 months (or 76cm), but I like that the Sirona Gi i-Size can be used rear-facing all the way up to four years old, which is the safest way for infants and toddlers to travel

While I think the 360-degree feature is a game-changer for parents, the mechanism can be quite stiff, which is the only thing that lets the Cybex Sirona Gi i-Size down. I have the similarly designed Joie i-Spin 360 as my main toddler car seat and it just pips the Sirona Gi to the post in this regard. 

Cybex Sirona Gi i-Size in 360-degree rotation

How we tested the Cybex Sirona Gi i-Size

  • Three months of using the Cybex Sirona Gi i-Size multiple times a week

  • Used on both short and long car journeys

  • Tested with a 18-month-old toddler

I tested the Cybex Sirona Gi i-Size car seat out with my now 18-month-old toddler. We used it at least three times a week during the 15-minute nursery run and for running short daily errands as well as on longer car journeys of 40 minutes or more. This was to see how comfortable the seat was over a longer duration.

As part of the testing process, I scored the car seat out of five in a number of different categories including: installation, safety and stability, ease of use, comfort, design, ease of cleaning and value for money.   

Read next: Best pushchairs to buy this year

Cybex Sirona Gi i-Size: what’s in the box?

  • Cybex Sirona Gi i-Size toddler car seat

  • Integrated ISOFIX base

  • User guide

While not included, the Cybex Sirona Gi i-Size is also compatible with the Cybex Car Seat Cup Holder, Cybex Sirona Gi i-Size Newborn Inlay and the Cybex SensorSafe 4-in-1 Kit, which acts as a temperature sensor and harness monitor among other things.

Cybex Sirona Gi i-Size accessories

Cybex cup holder
Cybex Car Seat Cup Holder

Buy now from Amazon
Cybex newborn inlay
Cybex Sirona Gi i-Size Newborn Inlay

Buy now from John Lewis
Cybex SensorSafe 4-in-1 kit
Cybex SensorSafe 4-in-1 Kit

Buy now from Amazon
Cybex Sirona Gi i-Size installation indicators

How easy is the Cybex Sirona Gi i-Size to install?

Installing the Cybex Sirona Gi i-Size is relatively easy. It has simple visual instructions stuck to the side of the seat so that you have them to hand at all times. There’s also a more detailed user guide included in the box. 

It took me 15 minutes to fully install the Sirona Gi i-Size as I initially had some trouble connecting the car seat base to the ISOFIX points in my Ford Fiesta. However, this was more an issue with the anchor points in my car than the car seat itself. 

I like that the Sirona Gi i-Size has helpful green and red installation indicators both on the base and the load leg. This reduces any margin for error, even if you’re in a rush, and offers reassurance that the car seat has been installed correctly. 

To install the car seat, you simply connect the integrated base to your car’s ISOFIX points before extending the load leg to the right height. The indicators will then turn green when both elements are correctly installed. 

Read next: The best car seats for 4-year-olds and beyond

Cybex Sirona Gi i-Size: how does it look?

The Cybex Sirona Gi i-Size is a car seat that will appeal to most families. The regular Gi i-Size comes in either Moon Black or Lava Grey, and has some small but aesthetically pleasing details on the cover.

I tested out the Plus version, which boasts additional mesh in the seat for added breathability. At £325 (versus £300 for the original), it’s slightly pricier than the normal Gi i-Size, but comes in three additional colourways: Ocean Blue, Beach Blue and Hibiscus Red. 

Mine was in Moon Black and I liked both the colour and design. For some contrast, it has white detailing on the edges of the harness pads as well as down the centre of the seat, which I thought was a nice touch. 

One of my favourite things about the Sirona Gi i-Size Plus is just how plush and padded the seat cover is. It feels lovely to the touch and ensured optimal comfort for my toddler on all car journeys.

Read next: The best lightweight buggies for babies and toddlers

Cybex Sirona Gi i-Size linear side impact protection

Is the Cybex Gi i-Size safe?

Yes! The Cybex Gi i-Size conforms to the R129 European car seat safety standard, which aims to improve car seat safety, particularly in the event of a side-impact collision. 

The R129 safety standard classifies child car seats based on height not weight, and performs side-impact crash tests as well frontal impact testing using state-of-the-art Q-type dummies which offer more accuracy. 

As part of this car seat regulation, it's mandatory for an R129 car seat to be rearward-facing until your child is a minimum of 15 months. However, one of the huge benefits of the Cybex Sirona Gi i-Size is that it goes even further and allows your child to sit rear-facing until four years old or 105cm. 

We know from car seat safety experts that rear-facing is the safest way for children to travel, so extended rear-facing car seats like the Sirona Gi i-Size are more than worth the investment.   

Aside from the benefits it offers in being an extended rear-facing seat, this car seat features integrated Linear Side-impact Protection (LSP), which offers increased safety in the event of a side-impact collision. Cybex has also used energy reduction technology to improve the safety performance of the Sirona Gi i-Size during forward-facing travel if you choose to forward-face from 15 months. 

Because it’s so new, the Sirona Gi i-Size hasn’t yet been tested by the German automobile club ADAC, which performs stringent safety tests. However, Cybex have done their own internal testing using the 2022 ADAC frontal crash test criteria. 

In terms of installation, the Cybex Sirona Gi i-Size feels sturdy in all its configurations, and the five-point harness is easy to buckle and tighten using the pull-strap. It then fits comfortably and stays firmly in place once tightened thanks to the strips on the underside of the shoulder pads, which nicely cling to your child’s clothes. 

Unlike the Joie i-Spin 360, the Sirona Gi-Size doesn’t have a mechanism in place to stop parents from turning the car seat into a forward-facing position before the recommended 15 months, however there is a clear safety sticker attached to the top of the car seat as a noticeable reminder.  

Cybex Sirona Gi i-Size harness

What's the Cybex Sirona Gi i-Size like to use day-to-day?

I was really impressed with how easy the Cybex Sirona Gi i-Size slotted into my family’s daily routine. The harness straps can be pinned to the side of the car seat once your child is out of the seat so that you can easily get your toddler in the seat for the next car journey. The pull-strap mechanism also ensures you can loosen and tighten the strap for easy in and out, even in a hurry. 

Less bulky than the Joie i-Spin 360, which I use daily with my toddler, the Cybex Sirona Gi i-Size fits well in the back of my small Ford Fiesta, although there is a limit to how much you can recline or move the front passenger or driver's seats. As my husband is 6’4”, this can prove an issue on longer car journeys. At 13kg, it’s also not a car seat you’d want to switch between cars regularly and, because of its ISOFIX base, you also won’t be able to use it on a plane. 

If you have twins or two under four, you’ll find it tricky to have two 360 spin car seats in the backseat at any one time. I tested this out by installing my Joie i-Spin 360 alongside the Sirona Gi i-Size and found that both car seats couldn’t be spun at the same time as there wasn’t enough room. This might have been different if I had a larger car. 

Despite this, the Sirona Gi i-Size is a car seat that’s been very well designed. By far its most useful feature is the 360-degree rotation, which, in my opinion, is a must for getting toddlers in and out of their car seat. With that said, the 360 mechanism is stiffer than that on the Joie i-Spin 360, and is the only real frustration I have with this seat. 

Because it’s an extended rear-facing seat, I find it reassuring to attach a car seat mirror to the headrest of the back seat so that my daughter is in view at all times. 

Read next: The best car sunshades for babies

How comfortable is the Cybex Sirona Gi i-Size?

As toddler car seats go, the Cybex Sirona Gi i-Size is one of the most comfortable I’ve tested. If you regularly travel long distances by car, you’ll likely want to upgrade to the Plus version because of the mesh fabric and all-round air ventilation system which offer greater breathability and help to keep your child cool, particularly during the warmer months. According to Cybex, the mesh “increases breathability up to six times compared to regular fabrics.”

My 18-month-old daughter enjoyed sitting in the car seat on both short and long journeys, especially as it’s similar in style to her usual car seat, the Joie i-Spin 360. However the Sirona Gi i-Size feels more comfortable for her to sit in thanks to the padding and mesh.

The seat can be adjusted easily to fit different heights as she grows by using a button at the back of the headrest, with 12 different settings to choose from. There are also five recline positions to choose from depending on preference, with a recline mechanism that’s smooth to operate.

While I wasn’t able to test how this car seat fared with a child at the top end of the age range (age four), I do feel there is enough leg room to keep my toddler comfortably rear-facing for as long as the car seat allows. 

Cybex Sirona Gi i-Size mesh seat padding

What’s the Cybex Sirona Gi i-Size like to use with a newborn?

While I didn’t personally test the Cybex Sirona Gi i-Size out with a newborn, the beauty of this car seat is that it can be used from birth with the cosy Cybex Sirona Gi car seat inlay (£45). If you don’t want to buy the newborn insert, you won’t be able to use the car seat until your baby is three months old or 61cm in height. 

Read next: Newborn essentials checklist

Is the Cybex Sirona Gi i-Size easy to clean?

Generally, yes. The Cybex Sirona Gi i-Size cover is machine-washable at 30 degrees. It took me some time to figure out how to remove the cover in its entirety, especially as there are a few different elements. I also needed to remind myself how I took the cover off so that it was easier to put back on again after washing. 

I like that the shoulder straps attach to the harness with poppers, which make them easy to remove for cleaning. As my seat is in Moon Black, stains are easily hidden, but for any that aren’t, I found it quicker and simpler to spot-clean the seat rather than remove the cover completely.  

Read next: The best baby carriers, wraps and slings

Cybex Sirona shoulder pads with poppers

Does the Cybex Sirona Gi i-Size offer good value for money?

Absolutely! The longevity of the Cybex Sirona Gi i-Size makes the car seat worth the cost, especially as it comes with an integrated base. It also retails at a similar price to many other 360 car seats on the market. 

While it doesn’t come with a newborn inlay as standard, it’s a good idea to buy this if you want to use the Sirona Gi i-Size as soon as your baby is born. 

It’s not essential to upgrade to the Cybex Sirona Gi i-Size Plus if your budget doesn’t allow it, however my toddler found the more breathable seat to be very comfortable, particularly during the summer when my car typically becomes a sweatbox. 

Granted, there are other top-performing 360 spin car seats out there like the Joie i-Spin 360, which retails slightly cheaper than the Sirona Gi i-Size, however I much prefer the seat padding on the latter. 

While the 360-degree mechanism could be smoother, this was still one of my favourite features. That, coupled with the extended rear-facing option and plush fabrics, makes the Sirona Gi i-Size more than worth its price tag in my opinion. 

About the author

Laura Westerman is an editor, writer and Deputy Head of Editorial Content at Mumsnet. Mum to a one-year-old, she’s always keen to make travel safe and fun for her daughter, so is fully invested in discovering the best and most affordable baby products on the market, and sharing her knowledge and findings with other parents.

With over seven years' experience as a full-time editor, five of which have been spent writing, commissioning and editing car seat reviews and round-ups, Laura has a keen eye for what parents love and likes nothing more than putting together honest reviews to make parents' lives that little bit easier. 

In addition to her work as a writer and editor, she has also appeared in a number of baby product videos for Mumsnet's YouTube channel.

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