- Suitable for children 61-105cm in height
- R129-compliant (i-Size ready)
- Isofix compatible
Keep your little one safe and snug with the Sirona Si rear-facing car seat. Designed for rear-facing travel up to 4.5 years, it offers up to 50% better protection*, a padded energy-absorbing shell, and Linear Side-impact Protection for 25% more side-impact safety**. The crotch pad and magnetic holders make boarding simple for parents and kids alike.
It comes with a Base S for a straightforward, ready-to-use setup, offering smooth one-handed 180° rotation for easy side entry. Simply turn the seat towards the car door to make loading and off-boarding easier, while reducing awkward lifts and making every journey more comfortable for both child and parent.
Rear-facing safety
Keep your little one safe and snug for the first 4.5 years. The shell acts like a protective shield, cleverly distributing impact forces and holding your child close. With rear-facing mandatory until 15 months, it provides up to 50%* better protection until they turn 4.5.
Grows up to 4.5 years
CYBEX GrowTech is specially designed to ensure that the seat grows and adapts with your child. The standard comfort inlay provides added support, while the newborn inlay (available separately) enables use from birth up to approximately 4.5 years (40–105 cm). AGR-certified for enhanced ergonomics, it features an adjustable headrest, M-position, and 40% more recline range in both rear-facing and more upright forward-facing positions**.
Use from birth
Three cleverly designed, removable inlays let you use the Sirona S car seat from Day 1. The Newborn insert and Newborn inlay (available separately) are for babies measuring 40 to 60cm, giving them the extra head and body support they need for a safe, snug fit. When your baby is no longer a newborn but still small, remove the Newborn insert and inlay but keep the Comfort inlay until they are 85cm tall. This soft, adaptive layer cushions and supports them as they grow and is included with the Sirona S car seat.
360° rotation
Smooth one-handed 360° rotation eases the strain on parents’ backs when placing your child in or taking them out of the car from the side. The rigid crotch pad provides easy and simple onboarding — quick and ergonomic for both parent and baby.
25% more side-impact protection
Advanced Linear Side-Impact Protection is part of a three-tier safety system that cuts impact forces by up to 25%*** by channelling energy into the car seat’s energy-absorbing shell and headrest. The integrated L.S.P folds out with a simple push during setup and tucks neatly away when space is limited.
Magentic belt holders
Clever magnets secure the buckle tongues to the sides of the Sirona S, keeping the belts neatly tucked away as you place your child in or remove them from the car seat. This streamlined entry creates a calm, effortless experience for both parent and child.
Optimal breathability
All-round air ventilation keeps the child cool and dry year-round. Innovative 3D mesh-style fabric that self-regulates moisture absorption, boosts airflow and ventilated hard parts guarantee optimal breathability and comfort. For extra peace of mind, Cybex offers SensorSafe, a child-in-car alert system that also monitors the car’s interior with an app that sends smartphone notifications.
Sun protection
XXL integrated sun canopy with UPF50+**** shields your child from the sun, cuts glare for safer naps, and keeps skin protected on the go. Breathable mesh window boosts airflow for better air circulation. Made with clever clips, the canopy can be easily detached, giving you the flexibility to adapt for every season, every trip, and every family adventure.
Soft on skin
Because your child deserves the best start to life, Cybex products are screened for harmful substances such as heavy metals, phthalates, flame retardants and other restricted chemicals before they reach you. Tests are done by internal labs and exceed regulatory testing standards in the markets.
Luxury design
The two-tone leather-look accents blend seamlessly with breathable mesh in this 'Style' version of the Sirona S, inspired by the finest luxury car interiors. The result is a sophisticated, refined look for you and sumptuous, secure comfort for your child.
*Compared to a forward-facing airbag seat in a frontal crash, based on internal testing.
**Compared to predecessor
***Confirmed by ADAC in its article dated 10 June 2026; referring to car seats of this type
****Except for mesh parts
Safety:
- Under no circumstances should a rearward-facing car seat be used on a passenger seat where there is an active airbag
- Correct fitting of all car seats and boosters is of paramount importance in making them the most effective in the event of an accident. Not all car seats fit all cars and it is important to check for fitting suitability on all cars you intend to fit the seat to, as well as re-checking if you change your car
- Always read the instruction booklet that comes with your car seat to achieve a safe and correct fitting, retaining the guide for future reference. We recommend fitting your car seat in advance of first using it
- We recommend that babies shouldn't be left in car seats (infant carriers) for prolonged periods
Suitability:
- Please make sure that you check the car seat you choose is suitable for your car before ordering. This can be done in store with a Partner or on the car seat manufacturer's website
- Some of our shops offer a car seat fit test, where a Nursery advisor will test the display model in your car to check that it will fit properly. Please contact your local shop to see if this service is available. Alternatively, please contact the car seat manufacturer who will be able to advise whether their model will be suitable for your car
- We also offer in-store and virtual appointments so you can access our All Things Baby services at a time and place to suit you. Click here to book your appointment. or find your nearest department store here
All the car seats in our range are designed to give your child the best possible protection and meet the criteria set out in the R129 (iSize) safety regulation. A baby must travel in the safer rear-facing position up to the minimum recommended age of 15 months. Some R129 car seats can be used rear-facing until a child is 105cm tall, which is around 4 years old.
Side impact testing is assessed as part of the regulation to improve the protection of the child’s head and neck. R129 also makes use of the most high-tech crash test dummies which not only has improved sensor technology to test for greater sensitivity, but it also features more sensors on fragile areas of the body. iSize is an enhancement of R129 that makes it easier to confirm your car seat's compatibility with any iSize approved vehicle - reducing the risk of installing your car seat incorrectly. While all i-Size car seats meet the R129 testing standards, not every R129 car seat is an iSize compatible seat.
R129 (iSize) car seats are classified by height only. The below table is a rough guide as to how the car seats can relate to a child’s age based on the average child's height. In some instances, we may still need to check the weight of the child within the height band due to the maximum mass load permitted on a vehicle’s ISOFIX points.
| Type | Height of Child | Approx. Age of Child |
|---|
| Baby | 40-85cm | Birth up to 15 months |
| Toddler | 40-105cm | Birth up to 4 years |
| Toddler | 40-150cm | Birth up to 12 years |
| Toddler | 76-150cm | 15 months up to 12 years |
| Child | 100-150cm | 4 to 12 years |
Note: This is a rough guide only. Please always refer to the individual car seat’s guidance for more specific details. Some car seats will be approved for use across two or more height bands. This just means that these seats have the ability to adapt as your child grows, meaning they can use them for longer.
