Cybex Sirona M
The Cybex Sirona M rear-faces up to 40 lb, forward-faces up to 65 lb, and is 20 in wide, per Cybex.
DiscontinuedNo longer made or sold new. Specs are kept for comparing generations.
- 40 lbRear-facing to
- 65 lbHarness to
- 24.7 lbSeat weight
- 20 inWidth
Sirona M: key facts
- The Cybex Sirona M rear-faces from 5 to 40 lb; forward-faces with a harness from 22 to 65 lb and up to 49 in tall, per Cybex.
- Outgrown by height: "Rear-facing: When top of head is at least 1 in. (2.5 cm) below the top of the Headrest. Forward-facing: When top of ears are below the top of the Headrest."
- It installs with LATCH rear-facing, seat belt rear-facing (lap/shoulder), lap belt rear-facing, LATCH forward-facing + top tether, seat belt forward-facing + top tether or lap belt forward-facing + top tether.
- Cybex says it expires 8 years after the date of manufacture.
- Cybex lists it as certified for aircraft ("This Restraint is Certified for Use in Motor Vehicles and Aircraft.").
- It's 20 in wide at the widest point and weighs 24.7 lb.
From Cybex's manual and published specs. Always follow the limits on your seat's labels.
How the Sirona M stacks up
Against the 40 convertible car seats we track. The shaded band is where the middle half of them fall; the dot is this one.
Below the typical range for convertible car seats (9 years to 10 years).
Within the typical range for convertible car seats (40 lb to 50 lb).
The same as most convertible car seats (65 lb).
Above the typical range for convertible car seats (17 in to 19 in).
Within the typical range for convertible car seats (21.6 lb to 27.9 lb).
Flying with the Sirona M
Cybex's label: “This Restraint is Certified for Use in Motor Vehicles and Aircraft.” It is 20 in wide at its widest point.
What airlines say about car seats:
- American: “Each ticketed customer is allowed 1 stroller and 1 car seat to be checked free of charge” “If an unoccupied, adjoining seat is not available, the gate agent will check the safety seat to your final destination.” Source
- Alaska: “We will transport your child's car seat and stroller free of charge as checked baggage.” Source
- JetBlue: “Checking a child safety seat will not count towards your checked baggage allowance and there is no fee assessed” Source
- Spirit: “One (1) car seat will be accepted per child as checked baggage at no charge.” Source
- Frontier: “strollers and car seats can be checked for free.” Source
- Allegiant: “There is no charge for checking or gate checking one car seat per fare-paying passenger.” Source
- Breeze: “Child seats may be carried on board the aircraft if a seat has been purchased for the Infant or Child” Source
Quoted from each airline's page as of 2026-11-02.
Where to buy the Sirona M
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- Discontinued. You may still find it used or on clearance.
- Check for recalls: Search the agency's recall list with the model number and date code from the label: NHTSA recall search.
- Car seat use and installation: see NHTSA's car seat page, which also lists free car seat inspection by certified technicians. Check the label and the maker's instructions, and ask your pediatrician about your child.
Full specs
| Cybex Sirona M | |
|---|---|
| Type | Convertible |
| Rear-facing weight | 5–40 lb |
| Forward-facing weight | 22–65 lb |
| Forward-facing height | Up to 49 in |
| Seat weight | 24.7 lb |
| Width | 20 in |
| Head rule | Rear-facing: When top of head is at least 1 in. (2.5 cm) below the top of the Headrest. Forward-facing: When top of ears are below the top of the Headrest. |
| Newborn insert | Newborn Insert, 5 lbs-11 lbs per manual chart; product page: 'The removable newborn insert provides support for babies from 5 lbs. to 11 lbs.' |
| Installation | LATCH rear-facing, seat belt rear-facing (lap/shoulder), lap belt rear-facing, LATCH forward-facing + top tether, seat belt forward-facing + top tether, lap belt forward-facing + top tether |
| Load leg | No |
| Rotates | No |
| Harness heights | 12 |
| Recline positions | 10 |
| Aircraft label | Certified for aircraft, per the maker |
| Expires after | 8 years |
Compare the Sirona M with
How each closest rival differs from the Sirona M, from the makers' specs.
- Joiechili spin 360rear-facing to 40 lbforward-facing to 65 lb
- 2 years longer before it expires
- 1.6 in narrower
- 2.4 lb heavier
- BritaxAdvocate ClickTightrear-facing to 40 lbforward-facing to 65 lb
- 2 years longer before it expires
- BritaxEmblem 3 Stagerear-facing to 40 lbforward-facing to 65 lb
- 1 years shorter before it expires
- UPPAbabyKnoxrear-facing to 45 lbforward-facing to 65 lb
- 2 years longer before it expires
- 5 lb higher rear-facing limit
Sirona M: questions answered
From Cybex's published specs, last checked 2026-11-06.
Does the Cybex Sirona M rear-face longer than other convertible seats?
20 of the 50 convertible seats we track rear-face to a higher weight than its 40 lb. The highest is the Axkid One 3 at 65 lb. NHTSA: stay rear-facing "until he or she reaches the top height or weight limit allowed by your car seat's manufacturer." (NHTSA)
Will the Cybex Sirona M fit three across or in a small car?
It's wider than 94% of the convertible seats we track, at 20 in. The narrowest is the WAYB Pico at 14.5 in. Fit depends on your vehicle; check each seat's manual and your vehicle manual. Car seat use and installation: see NHTSA's car seat page, which also lists free car seat inspection by certified technicians. Check the label and the maker's instructions, and ask your pediatrician about your child.
Can you bring the Cybex Sirona M on a plane?
Yes, Cybex lists it as certified for aircraft; look for the red-lettered label that says so. The FAA asks that a car seat go in a window seat so it doesn't block the aisle, and the crew will look for that label. It weighs 24.7 lb to carry through the airport.
Sirona M or chili spin 360: what's different?
By the makers' specs, the chili spin 360 has a rotating seat. See every spec side by side.
Is it OK to buy a used Sirona M?
NHTSA publishes guidance on used car seats on its car seat page. Cybex lists a lifespan of 8 years from manufacture for this model. Check the label and the maker's instructions, and ask your pediatrician about your child.
Still wondering? Write to us at hello@cribpicks.com and we'll look it up.
More convertible car seats
- Orbit BabyG5 Toddlerrear-facing to 35 lbforward-facing to 65 lb
- NunaREVVrear-facing to 30 lbforward-facing to 40 lb
- UPPAbabyRoverear-facing to 50 lbforward-facing to 65 lb
- ChiccoNextFit Max ClearTexrear-facing to 50 lbforward-facing to 65 lb
- BabyarkSmartrear-facing to 50 lbforward-facing to 65 lb$990
- NunaREVV maxxrear-facing to 40 lbforward-facing to 65 lb$800
Where these specs come from
Last checked 2026-11-06. Spot something wrong? Tell us. Read our editorial and safety policy and corrections.