Cybex Sirona S i-Size Car Seat (3 Months–4.5 Years)

Cybex

Comfort Sepia Black

Comfort Cozy Beige

Style Sepia Black

Style Opal Blue

Style Misty Grey

Style Amber Brown

Style Quartz Pink

Style Jade Green

Style Off White

€389.95

This product will be released on 31 December 2026

Product number: 526002921

Free shipping on orders over € 50

4.8 / 5 stars on Trusted Shops

14-day right of return

10% newsletter discount on RRP prices

Safety: Rear-facing travel up to 4.5 years offers up to 50% more safety
Easy Entry: 360-degree one-hand rotation spares your back every day
Protection: Advanced L.S.P. system reduces side impact forces by 25%
Ergonomics: AGR-certified GrowTech design expands with your growing child
Convenience: Magnetic belt holders keep harness buckles cleanly out of the way
Breathability: Innovative 3D mesh fabric ensures 6x better airflow on trips

Description

Cybex Sirona S i-Size: Maximum Safety for Your Child

Are you looking for a car seat that provides your little one with maximum protection and security on every journey? The Cybex Sirona S i-Size car seat (61–105 cm) offers the highest level of rear-facing travel from approximately 3 months up to 4.5 years of age (max. 20 kg). During the first years of life, the rear-facing position provides optimal protection for your child's delicate head and neck: The robust seat shell acts like a protective cocoon, distributing impact forces effectively and reducing the risk of injury by up to 50% compared to forward-facing car seats. With an optionally available newborn insert, the Sirona S can even be used right from birth (40–60 cm).

Effortless Handling and Ergonomic Comfort

360° Rotation & Easy-In Harness System

Everyday family life can be hectic – but fastening your child's harness doesn't have to be! Thanks to its smooth 360° rotation, the Sirona S can be effortlessly turned towards the open car door with just one hand when installed on the compatible Base S. This takes the strain off your back and makes placing your child in the seat considerably easier. Cleverly designed details make handling even more convenient: The Easy-In harness buckle stays upright on its own, while integrated magnetic harness holders keep the shoulder straps secured to the sides. This keeps everything out of the way when getting your child into the seat, allowing you to fasten the harness securely in seconds.

CYBEX GrowTech & AGR Certification

Children grow quickly, and the Sirona S grows effortlessly with them. The intelligent CYBEX GrowTech system provides an ergonomically excellent sitting and reclining position, certified and recommended by Aktion Gesunder Rücken (AGR). With a 40% greater adjustment range for reclining positions – both rear-facing and forward-facing – your child can always find the ideal position for a relaxing nap on the road. The included comfort insert also supports the healthy M-position of the legs and provides gentle support as your child grows.

Reliable Protection & Excellent Seat Ventilation

Safety meets modern climate comfort. The Linear Side-impact Protection system (L.S.P.), together with the energy-absorbing seat shell, forms a strong three-stage safety concept that reduces side-impact forces in an accident by approximately 25%. Integrated all-round ventilation ensures pleasant temperatures during summer. The exclusive Style models feature innovative 3D mesh fabric that improves air circulation by up to six times compared to conventional fabrics and effectively regulates moisture. An integrated XXL sun canopy (available exclusively in the Style models) with UPF50+ also protects your child's delicate skin from glare and sunlight. In addition, the Sirona S can be seamlessly used as the successor to the Cloud S infant car seat on the same Base S.

All Product Details at a Glance

Feature	Specification
Child Height & Age	61–105 cm (approx. 3 months to 4.5 years; from birth at 40–60 cm with the optional newborn insert)
Maximum Weight	Up to 20 kg
Safety Standard	UN R129/04 (i-Size)
Seat Weight	7.5 kg (Comfort) \| 7.8 kg (Style)
Dimensions (L x W x H)	560 x 450 x 550 mm
Safety Features	Up to 50% safer rear-facing car seat, L.S.P. side-impact protection (25% more protection)
Comfort Features	360° rotation, AGR-certified design, magnetic harness holders, Easy-In harness buckle
Compatible Base	CYBEX Base S (sold separately)

Kindermaxx Verdict

The Cybex Sirona S i-Size impresses in every respect as an exceptionally safe and thoughtfully designed rear-facing car seat for toddlers. The combination of extended rear-facing travel up to 4.5 years, back-friendly 360° rotation and clever everyday features such as magnetic harness holders makes every journey more relaxed. Together with its outstanding AGR ergonomics ratings and excellent ventilation, the Sirona S is a first-class choice for discerning parents!

Product properties

Age:	3+ months
Attachment:	with Isofix
Direction of travel:	Backward, Forward
Securing with:	5 - Point Harness

Frequently Asked Questions

With the separately available newborn insert (40–60 cm), the Sirona S i-Size can be used from birth. Without the insert, it is suitable from approximately 61 cm (around 3 months).

Yes, the Base S is essential for ISOFIX installation and the 360° rotation function. It is not included as standard and must be purchased separately.

First, attach the Base S to your vehicle’s ISOFIX anchors and secure it until the indicators turn green. Then simply click the Sirona S i-Size onto the Base S. Before every journey, check that all locks are securely engaged.

For maximum protection, Cybex recommends keeping the seat rearward-facing for as long as possible—ideally up to the upper height limit of 105 cm (20 kg). Only switch to forward-facing once your child is older or if space constraints require it.

By pressing the release button, you can rotate the Sirona S i-Size toward the car door with one hand. This lets you place your child in the seat with less strain on your back, maintain full access to the Easy-In harness system, and fasten the 5-point harness comfortably.