I found the following description regarding the difference: "I am the Cybex Solution S I-Fix and differ from the Solution S-Fix by the i-Size standard. This standard ensures that much more is demanded of me in crash tests than of the normal S-Fix. The criterion in these tests is not the weight, but the size of the child. I can be used from the age of 3 until your child is about 12 years old. My patented headrest, which can be adjusted in height and inclination 12 times, prevents your child's head from tilting forward when he or she is asleep. This keeps your child's head in the safety zone even during an accident. With the integrated linear side impact protection, I offer your treasure the highest level of safety in the event of a side impact, because when it is folded out, it ensures that the forces acting on your child are reduced by up to 25%. My optimised ventilation system is particularly comfortable and ensures that the seat climate always remains optimal. I am connected to your car via the ISOFIX system, so I am even safer in the event of an accident."

This is the model: s i-fix navy - blue - 15 kg to 36 kg (3-12 years) approved by r129/03 - Patented reclining headrest, prevents the child's head from tilting forward. - Height adjustment in 12 positions The S2 i-Fix : - From 15 kg to 50 kg - From 3 years to 12 years - Patented tiltable headrest prevents the child's head from tilting forward. - Height adjustment in 12 positions In the end, the models are similar, only the weight margin is greater on the second version.

I think the height of the child is specified for the I-fix. 100 - 150 cm. At 4.5 years old, your child should be the required height. You might want to check the Cybex homepage for more information.

Yes, and the seat is comfortable. after that the head support is much better during the trip than the competition but well it's not 100% true. Sometimes my daughter falls asleep with her head hanging down and I have to pull her up 😅

No, unfortunately this is not possible, as this product is supplied exclusively to the specialist trade.

Unfortunately, we have not been able to find any information on this.

According to our information, this is fixed.