Britax Baby-Safe i-Size Review – EU Car Seat

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Britax Baby-Safe i-Size

In 2013 European car seat laws were overhauled to ensure safer, easier to use products for caregivers. As part of a 3-phase plan, rear facing only infant seats were the first to benefit from the new rules. The Baby-Safe i-Size is one of Britax Römer’s i-Size compliant infant seats. When paired with the Flex base it features some very interesting elements. Let’s take a closer look!

CSFTL Quick Stats

  • Weight range: 0-13 kg (0-29 pounds)
  • Height range: 40-83 cm (16-33 inches)
  • Lowest Harness Position: 19 cm (7.5 inches) with infant insert
  • Expiration: Britax doesn’t specify a maximum period of use
  • Handle Position: The handle must be upright and locked in the vehicle


  • Weight (carrier only): 4.8 kg (almost 11 pounds)
  • Width of carrier at widest point: 44.5 cm (17.5 inches); add 5.5 cm (about 2 inches) for a fully extended SICT
  • Width of base at widest point: 44 cm (17 inches)


Infant Insert

Britax Baby-Safe i-Size insert

The infant insert is one piece with both head and torso support. The torso portion includes two removable polystyrene blocks. These blocks increase support and side impact protection for the very smallest of passengers, keeping them nice and snug in those early weeks.

Britax recommends that the blocks stay in until the baby is big enough for the harness to be moved from the lowest setting, though I found my son was already too wide to fit comfortably with the blocks in when he was 6 weeks old. The rest of the insert can be removed when the baby has good head control and no longer fits comfortably with the insert in the seat.

Lie Flat Positioning

Britax Baby-Safe i-Size “lie flat” positioning

Very young babies have poor head control, which means an upright angle in a car seat can be dangerous. Unable to lift their heads, their airway can be compromised if they’re sat up too much. However, during a crash an upright angle is safer for bigger babies.

Britax has reconciled these needs by having the angle of the seat back change as the harness is raised. On the lowest setting the baby is kept at a more reclined angle with the pelvis more forward — Britax calls it a lie-flat angle, though it is not actually completely flat — while the angle becomes more upright on higher harness settings.

Flex Base

Britax Baby-Safe i-Size Flex base

The Flex base is extremely solid. Weighing in at 8.7 kg (about 19 pounds), it takes some muscle to carry it around! It features ISOFIX arms, a load leg and, most intriguing, a level indicator that helps ensure the carrier portion of the seat is at the correct angle. This built-in level indicator is absent from most European car seats. The level indicator negates the need for an app or tool to ensure the car seat is at the optimum maximum of 45 degrees for newborns. The angle of the base is also adjustable to help compensate for the angle of the vehicle seat.

The downside of the Flex base is that there are no follow-on seats that can use it — it’s only suitable for the Baby-Safe i-Size seats, which doesn’t make it a very budget friendly option.


The cover of the Baby-Safe i-Size can be removed and washed at 30 degrees. It also wipes down very well for smaller cleaning jobs. A huge range of colours is available, and a summer cover can be purchased separately.

The fabric used for the cover isn’t very breathable — my son has been rather sweaty in the warmer weather!

Sun Canopy

Britax Baby-Safe i-Size canopy

The sun canopy offers UPF 50+ sun protection. It attaches to hooks on the handle, meaning it cannot be independently raised. This can make it a bit frustrating when you want to quickly lower or raise the canopy. Its coverage is adequate and it does a reasonable job keeping sun out of sensitive eyes.

Side Impact Protection

Britax Baby-Safe i-Size side impact protection

The Baby-Safe i-Size features extendable side impact protection screws. They’re used on the side of the car seat closest to the door and serve to absorb some of the forces during a side impact crash.

I wish the side impact protection was a bit easier to use. When the screws is extended, it makes the carrier difficult to get in and out of the base. Plus, it adds another step to using the seat that can easily be forgotten. While it takes only a few seconds to screw it in and out, it’s the last thing on your mind when you’re standing in the pouring rain trying to get everyone situated in the car!

Installation: With the Flex Base

The Flex base can only be installed with ISOFIX. Pull the load leg out from under the seat. Next, pull the lever in the centre of the base to extend the ISOFIX arms. Line up the arms with the ISOFIX anchors in the vehicle seat — if the anchors in your vehicle are difficult to access, attach the included ISOFIX guides to them to make it easier to attach the ISOFIX arms. Press the arms into the anchors until they click and the indicators on the arms show green. Push the base into the vehicle seat back until it makes firm contact.

Britax Baby-Safe i-Size Flex base

Ensure the load leg has been fully rotated out from the base — the red indicator at the top should no longer be visible. Press the buttons on the load leg and pull down on the bottom to extend it to the floor of the vehicle. The indicator on the bottom of the leg will show green when it’s sufficiently extended.

Britax Baby-Safe i-Size Flex base angle adjustment button

Finally, press down on the angle adjustment button and raise or lower the base until the indicator is entirely green. In our BMW i3 we needed it one click up for the indicator to turn green.

Britax Baby-Safe i-Size carrier attachment indicator

The carrier portion of the seat clicks easily onto the Flex base. Line up the attachment points at the sides of the carrier with the points on the base and click it in. An indicator on each side turns green when the seat is clicked in correctly.

Unscrew the side impact protection on the side of the seat closest to the door. Extend it until it is 5 mm from the door or it is fully extended.

Britax Baby-Safe i-Size carrier removal handle

To remove the carrier, pull on the handle at the back top of the carrier with one hand and use the other hand to lift the carrier off the base.

Installation: Without the Base

Britax Baby-Safe i-Size baseless install

The carrier portion of the seat can be installed without the base. To install it this way,
first place the carrier on the vehicle seat. Then, thread the lap portion of the vehicle seat belt through the dark blue belt guides and over the top of the carrier. Next, buckle the vehicle seat belt, then thread the shoulder portion around the back of the seat and into the lighter blue belt guide. Press down on the seat while pulling the shoulder portion of the vehicle seat belt tight. Unscrew the side impact protection on the side of the seat closest to the door.

I found it difficult to get a secure baseless install in our Ford Focus. When the seat was at a good angle for a newborn, it moved too much at the belt path. At a more upright angle the installation was extremely stable, but I wouldn’t have been comfortable allowing a newborn to ride in it.

Adjusting Harness Height

Britax Baby-Safe i-Size harness adjustment

Britax advises that the harness should be approximately 25 mm (1 inch) below the child’s shoulders. To adjust the harness height, take baby out of the seat and disengage the buckle. Open the door at the back of the seat — inside is the manual storage as well as the harness adjuster. Press in on the button and slide the adjuster up or down. I found this very difficult to do with one hand, as the adjuster button and slide were both very stiff. Make sure the button locks into place — you’ll feel it pop back out — once you’ve selected the correct height.

Fit to Child

6 Weeks Old

Britax Baby-Safe i-Size — 6 week old fit

Our model is 6 weeks old. He weighs 5 kg (11 pounds) and is about 54 cm (21 inches) tall. He’s already too wide to fit comfortably with the polystyrene blocks, so they’ve been removed.

With the harness on the lowest setting and the rest of the insert in, the straps are at just the right height. I did find it difficult to loosen the harness enough at this setting — it catches on the harness adjuster in the back and doesn’t loosen as much as it otherwise could. I predict this will get easier as the harness is moved up.

The biggest challenge so far has been buckling the harness. The buckle pad is part of the cover, so it can’t be removed or adjusted out of the way. It frequently interferes with the buckle tongues, making it very difficult to buckle. In addition, the crotch strap seems very short, so maneuvering around the short strap and the buckle pad has been very challenging.

Once buckled, though, he seems comfy in the seat and his head doesn’t slump.

3 Months Old

Britax Baby-Safe i-Size — 3 month old fit

Here’s our same model at 3 months old. He’s now up to 6.8 kg and 61 cm, so he’s higher on the weight charts and just about average height. He still has the insert in, but he’s quickly growing too big for it. He’s moved up to the second harness setting, but once the insert is removed he’ll need to go back down to the first setting.

As predicted, it’s easier to loosen the harness sufficiently at this setting. Buckling is also less challenging with more slack in the harness to work with. It’s easy to tighten the harness — I pull down on the harness covers and retighten to ensure they haven’t interfered — and he gets an excellent fit.

Important Information: Where to Find

Expiration: Britax doesn’t specify a maximum period of use.

Britax Baby-Safe i-Size manual storage

Manual Storage: A compartment at the back of the carrier holds the manual. The seat ships with the manual translated into 28 languages, but only one of them should be stored in the compartment at a time.

The Flex Base has a manual storage area towards the ISOFIX end of the base.

Airplane Approval: The Baby-Safe i-Size is not approved for airplane use. However, the Baby-Safe2 i-Size, which is largely identical, is approved for use onboard aircraft. The Flex Base cannot be used on a plane.


The Baby-Safe i-Size with Flex base is a solid, well made (if heavy!) seat. It’s comfortable and cosy for the tiniest passengers, but does have some ease of use issues, especially at the lowest harness setting. When used in conjunction with the Flex base it is extremely easy to install and take in and out of the vehicle. However, its baseless install was a bit more problematic. The excellent features of the Flex base more than make up for the niggling ease of use issues for the carrier itself.

Note: The Baby-Safe2 i-Size is largely identical to the Baby-Safe i-Size — the only differences noted by Britax are airplane approval and darker blue belt guides.