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Cybex Sirona S

The Cybex Sirona S rear-faces up to 50 lb, forward-faces up to 65 lb, and is 19 in wide, per Cybex. A rotating Cybex convertible with a height-adjustable load leg, anti-rebound design and a one-time belt installation for both directions.

DiscontinuedNo longer made or sold new. Specs are kept for comparing generations.

  • $549.95List price
  • 50 lbRear-facing to
  • 65 lbHarness to
  • 30.4 lbSeat weight
See it on Cybex's site

When does it expire?

All convertible car seats

Sirona S: key facts

  • The Cybex Sirona S rear-faces from 4 to 50 lb and up to 49 in tall; forward-faces with a harness from 22 to 65 lb and up to 49 in tall, per Cybex.
  • Outgrown by height: "Rear-facing: CHILD’S HEAD MUST BE 2.5 CM (1 IN) OR MORE BELOW THE TOP OF THE HEADREST OR SHELL, WHICHEVER IS HIGHER. Forward-facing: Top of ears below the top of the Headrest."
  • It installs with seat belt.
  • Cybex says it expires 10 years after the date of manufacture.
  • Cybex says it isn't certified for aircraft.
  • It's 19 in wide at the widest point and weighs 30.4 lb.

From Cybex's manual and published specs. Always follow the limits on your seat's labels.

How the Sirona S 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.

Expiration10 years

Within the typical range for convertible car seats (9 years to 10 years).

This one
7 yearsmiddle 10 years10 years
Rear-facing limit50 lb2nd highest rear-facing limit of 39

Within the typical range for convertible car seats (40 lb to 50 lb).

This one
35 lbmiddle 40 lb65 lb
Forward-facing limit65 lbHighest forward-facing limit of 39 convertible car seats

The same as most convertible car seats (65 lb).

This one
40 lbmiddle 65 lb65 lb
Width19 in22nd narrowest of 29

Within the typical range for convertible car seats (17 in to 19 in).

This one
14.5 inmiddle 17.8 in23.5 in
Weight30.4 lb24th lightest of 26

Above the typical range for convertible car seats (21.6 lb to 28 lb).

This one
8 lbmiddle 26 lb31.3 lb
Price$549.9531st lowest price of 38

Above the typical range for convertible car seats ($129.99 to $500).

This one
$59.99middle $399.99$990

Listed features

  • 360-degree swivel
  • Load leg and anti-rebound design
  • Rear-facing to 50 lb

Worth checking

  • Heavy at 30.4 lb
  • List price $549.95
  • No booster mode

Where to buy the Sirona S

Prices and availability change. We may earn a commission from some links.

good to know
  • 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 S
TypeConvertible
List price$549.95
Rear-facing weight4–50 lb
Rear-facing heightUp to 49 in
Forward-facing weight22–65 lb
Forward-facing heightUp to 49 in
Seat weight30.4 lb
Width19 in
Head ruleRear-facing: CHILD’S HEAD MUST BE 2.5 CM (1 IN) OR MORE BELOW THE TOP OF THE HEADREST OR SHELL, WHICHEVER IS HIGHER. Forward-facing: Top of ears below the top of the Headrest.
Newborn insertNewborn Insert and Newborn Headpad Insert ('To ensure a better fit for smaller infants, the Newborn Insert may be needed'); manual gives no weight limit for the insert
Installationseat belt
Load legYes
Anti-rebound barYes
RotatesYes
Harness heights12
Recline positions12
Aircraft labelNot certified for aircraft
Expires after10 years

Compare the Sirona S with

How each closest rival differs from the Sirona S, from the makers' specs.

Ask the meadow

Sirona S: questions answered

From Cybex's published specs, last checked 2026-11-06.

Does the Cybex Sirona S rear-face longer than other convertible seats?

1 of the 50 convertible seats we track rear-face to a higher weight than its 50 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 S fit three across or in a small car?

It's wider than 85% of the convertible seats we track, at 19 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 S on a plane?

Cybex doesn't list it as certified for aircraft, so it can be checked as luggage but not used in the plane seat. See seats approved for planes.

Sirona S or RAVA next: what's different?

By the makers' specs, the Sirona S has a load leg; the Sirona S has an anti-rebound bar; the Sirona S has a rotating seat; the RAVA next has no added flame retardants (maker's claim); the RAVA next lists for $24.95 less. See every spec side by side.

Is it OK to buy a used Sirona S?

NHTSA publishes guidance on used car seats on its car seat page. Cybex lists a lifespan of 10 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

  • NunaRAVArear-facing to 50 lbforward-facing to 65 lb$480
  • EvenfloGold Revolve360 Slimrear-facing to 50 lbforward-facing to 65 lb$449.99
  • ClekFoonfrear-facing to 50 lbforward-facing to 65 lb$649.99
  • BritaxGalaxy360 Slimrear-facing to 50 lbforward-facing to 65 lb$429.99
  • WAYBPicoforward-facing to 50 lb14.5 in wide$499
  • ChiccoFit360 Zip ClearTexrear-facing to 40 lbforward-facing to 65 lb$489.99

Where these specs come from

Last checked 2026-11-06. Spot something wrong? Tell us. Read our editorial and safety policy and corrections.