European Booster Seat Review: Casualplay BackFix i-Size Review

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CasualPlay BackFix i-Size highest headrest position

CasualPlay BackFix i-Size highest headrest position

It isn’t often that we see a new seat that truly makes us turn our heads and go “Wow!” But the Casualplay BackFix i-Size is one of those seats. As a completely new concept, it is neither a high back booster nor a backless booster, but something in between. Rather than boosting the kiddo up to fit the adult seat belt, it brings the adult seat belt down to fit the child.

By eliminating the booster part of the seat, BackFix i-Size fits in much smaller spaces than traditional booster seats. We definitely wanted to try it out! Casualplay was kind enough to provide us with a seat to try, and on our first long-distance car journey in several years we put the BackFix i-Size to the test.

CasualPlay BackFix i-Size lowest headrest position

CasualPlay BackFix i-Size lowest headrest position

CSFTL Quick Stats

  • Weight range: There are no weight limits for the seat
  • Height range: Overall height of 100-150 cm
  • Lowest belt guide position: 36 cm
  • Highest belt guide position: 53 cm
  • CasualPlay recommends that you replace the BackFix i-Size after any crash.


  • Width of seating area (at lap belt guides): 32 cm
  • Width at widest point of seat (shoulder area): 47.5 cm
  • Shoulder area measurement: 35.5 cm
  • Weight of booster: 5 kg


  • R129 certified
  • Memory foam in headrest
  • ISOFIX installation
  • Recline settings
  • No base – child sits on the vehicle seat

i-Size All the Way

Unlike most other i-Size boosters on the market, the Backfix i-Size is i-Size compliant for its entire period of use. This means that, unlike most high back boosters which become “vehicle specific” after around 130 cm, the Backfix fits in the imaginary box dictated by i-Size regulations until it’s outgrown.

ISOFIX Required

Most Isofix booster seats can also be used without ISOFIX by leaving the ISOFIX stowed and simply buckling the child in the seat. However, due to its unique nature, the Backfix requires ISOFIX  – it cannot be used in a seating position that does not have ISOFIX anchors for installation.

Optional Bits

The seat pad attaches to the BackFix with two poppers.

The seat pad attaches to the BackFix with two poppers.

Some versions of the Backfix come with a seat belt pad for the shoulder belt. This pad is optional, and our model did not come with one. In addition, the bottom seat pad is optional. It’s attached via poppers (aka snaps for our American readers) and can be removed if desired.


The headrest includes memory foam on the sides. It’s a fairly tight fit around the head, but our main model didn’t mind. He found the headrest very soft and comfortable, and he was able to easily fall asleep on a long journey.


CasualPlay BackFix i-Size recline lever

Press the lever with your thumb, then pull the seat out on the Isofix arms.

The BackFix i-Size features two recline positions in addition to the upright position. To change the recline, put your thumb in the hole in the seat backrest, then grab the bottom of the backrest with the rest of your hand. Use your thumb to press the lever in the hole, and pull the bottom of the backrest out. This will pull the seat out on the ISOFIX arms. Release the lever, then push or pull the backrest to make sure it’s locked into one of the three positions. Make sure that the top of the BackFix is still in contact with the vehicle seat back.

I did find that it wasn’t always easy to find the middle recline position, though it didn’t seem entirely necessary – my son was quite happy with the full recline!

Belt Guides

The shoulder belt guides on the Backfix are pretty standard. The lap belt guides, however, are unique. Since the seat isn’t boosting the child up to achieve a good belt fit, the lap belt guides are instead holding the seat belt down to properly fit the child. This means that the guides are very thick plastic, and the belt path is quite narrow to prevent the seat belt from coming out of position. On the buckle side, both the lap and shoulder belt must go through the lap belt guide; this can be a bit tricky due to how tight the belt guide is. However, with a little practice, most older kids should get the hang of it pretty quickly.


CasualPlay BackFix i-Size Isofix indicators

Make sure the ISOFIX indicators are green

The BackFix i-Size MUST be installed with ISOFIX. Line up the ISOFIX arms with the ISOFIX anchors in the vehicle and push each one on until they click and the indicator on the arm shows green. Make sure the top of the booster rests against the vehicle seat.

CasualPlay BackFix i-Size headrest adjustment loop

Pull the loop to unlock the headrest and adjust up or down.

Pull the loop at the top of the headrest to unlock it, then move it up or down to position the shoulder belt guide .5 to 2.5 cm above the child’s shoulders. The shoulder belt should be centered between the neck and the outside of the shoulder, without hovering.

CasualPlay BackFix i-Size belt guide

Make sure the seat belt isn’t twisted in the belt guides.

Finally, slide the vehicle seat belt into the belt guides. Make sure the shoulder belt isn’t twisted after sliding it into the shoulder belt guide. For the lap belt, slide it into the lap belt guide on the opposite side of the buckle. Make sure there are no twists.

Fit to Child

4.5 Years Old

4.5 year old in the CasualPlay BackFix i-Size

4.5 year old in the BackFix

Our 4.5 year old model weighs about 16 kg and is 104 cm tall. He’s too immature to use a booster yet, but since he meets the 100 cm minimum height for the BackFix we thought we’d try out his fit in it. Please note that we continue to advocate that children be at least five years old before moving to a booster seat.

With the headrest on the lowest setting, he still isn’t yet tall enough to get a safe vehicle seat belt fit. The shoulder belt guide is too high. He’s got quite a bit of growing to do before he’s big enough for this seat, but he’ll stay harnessed for now since he doesn’t weigh enough and isn’t yet old enough to safely use a booster.

9 Years Old

9 year old in the CasualPlay BackFix i-Size

9 year old in the BackFix

Our 9 year old model is around 28 kg and 131 cm tall. He highly rates the Backfix. His belt fit is excellent, with the lap belt low, touching the thighs, and the shoulder belt nicely centered over his shoulder. He finds the seat very comfortable – due to its low profile, his feet can rest easily on the floor of the vehicle, and he finds the vehicle seat much softer and more comfortable than the lightly padded plastic on many boosters. The headrest was a bit tight around his head, but he likes how cushy the padding is. He tried the seat both with and without the optional bottom pad, and preferred it with the pad. Without the pad he found that the ridges in the upholstery of the vehicle seat were uncomfortable.

The only issue he had with the Backfix was that it’s more fiddly for him to buckle up on his own. Getting both the lap and shoulder belt into the belt guide near the buckle was sometimes a bit tricky – I had to coach him to make sure the lap belt wasn’t folded before he put the shoulder belt into the guide. He also occasionally got frustrated when trying to unbuckle quickly, as getting the seat belt out of the guide was also tricky – he needed to focus on what he was doing rather than just hopping out of the car.

10 Years Old

We did find a camera-shy 10 year old to help us test the seat. At 38 kg and 145 cm tall with broad shoulders, he’s nearing the top end of the limits for the Backfix. He only tried the seat briefly, but he noted that he found it too narrow through the shoulders to be comfortable. He did have some growing room left in terms of headrest height, and his belt fit was good, but the shoulder issue meant he would not have been happy to use the seat. Children who are less broad through the shoulders are more likely to fit the BackFix for the full 150 cm.

Important Information: Where to Find

Expiration: CasualPlay doesn’t mention a maximum period of use in their manual, but it does say “We guarantee the safety of the product when it is used by the original buyer, do not use second hand safety products or restraint systems.”

Handy manual storage pocket on the CasualPlay BackFix i-Size

Handy manual storage pocket on the BackFix

Manual storage: Unzipping the zip at the back of the seat will reveal a mesh pocket for storing the manual; a label on the cover indicates where the storage pocket is. We love it when seats have a dedicated spot for storing the manual!

Airline Approval: As with most booster seats, the BackFix is not approved for use in aircraft because airplanes typically only have a lap belt and booster seats require a lap and shoulder belt. Due to its light weight and relatively small size, the BackFix could make a good travel option. Unfortunately, it does not fold up.


The BackFix i-Size is an excellent option for vehicles with sloping ceilings or limited cabin space. In these vehicles, the shape of the ceiling makes it difficult or impossible to keep children in high back boosters until they’re ready for the adult seat belt. By offering the protection and support of a high back booster but with a much lower profile, the BackFix is an excellent option for keeping kids better protected for longer in circumstances where they might otherwise have to move to a backless booster much earlier. As a standard everyday booster in larger vehicles, it is more likely to accommodate three across, but it isn’t as intuitive or easy to use as a standard booster. We still love that there’s an option for those smaller vehicles, though, and are thrilled that this option is available!