Cybex Eternis S vs Sirona M

Our vehicle is convenient to transport goods and people but the fact that there is a high risk of accidents on the road makes us parents worried about the safety of our children. For those whose babies are going to be transported since early age, Cybex Eternis S Vs Sirona M will be two ideal options to consider. These convertible car seats are convenient but also different and before deciding to choose one, go check what you need to know about the models below.

In this article, we are going to give you information about:

  • When and What Car Seat to Choose
  • What are Cybex Eternis S and Sirona M
  • What Cybex Eternis S and Sirona M Look Like
  • How are the Installation of Cybex Eternis S and Sirona M
  • How are the Fit of Cybex Eternis S and Sirona M
  • What else Cybex Eternis S and Sirona M can offer
  • Cybex Eternis S Vs Sirona M

Car Seat Across the Age

Having a baby doesn’t mean we have to stay at home all the time because chances are you will also want to take them out there including for the routine check up to their pediatrician. Having a private vehicle is awesome as you can transport both people and goods conveniently but, just like any moving object, their moderate to high risk of accident can often be concerning for parents. To help your vehicle become safer for our little one, we should install a proper car seat for their age.

Car seats are made to assist the car’s standard safety system in keeping your children safe despite how they are not build for their small bodies. They are also required and mandatory to be used when children is on board in almost any states in the country. Depending on each state’s law however, the minimum age they can start using a seat belt may vary but usually they are around the age of 12 or 13 when ready to say goodbye to their car seat.

Our children should use car seat since day one and the first car seat they can use are either infant car seat or convertible seat but for young babies who can’t support their neck and had yet many parents prefer to use the infant seat as it conforms to their body better and can be mounted on stroller frame as well. Typically, infant car seats can last for around a year until they have to use convertible car seats which can be installed both in the rear and front facing position.

When the children are around 2 to 4 years old or following the seat recommendation, they can start using the front facing position where the seat is secured using a seatbelt or tether. In this position children can still use their harness and similarly, children can keep this seating procedure until they are reaching the age of 5 or until reaching the maximum weight and height recommendation from the seat manufacturer. The next step is they should be ready for a booster seat and in this scenario, the car’s seat belt is used to secure the children.

Boosters as the name suggests only aid the height and weight of the passenger so they can fit nicely on the seatbelt. Some booster seats use backrests the same to the front facing scenario with differences only on what securing the children. A booster seat often has a height limit of 145 cm tall in which after, our kid should be able to use the seatbelt without any accessories.

 Cybex Eternis SCybex Sirona M
Product Dimensions25.3 x 20 x 25.5 inches
29 x 20 x 18.5 inches
Shipping Weight26 pounds
24.7 pounds
Best offerCheck priceCheck price

About Cybex Eternis S and Sirona M

If you are here then it means parents are currently looking for a car seat that can be used since early days but will also last until a few years later. This application calls for convertible car seats and there are lots of them out there. In general, all car seats need to meet the standard for safety reasons and they are safe when installed properly. The price difference often indicates that some are packed with more features to make the application more convenient.

Car seats for children are offered by various companies in the market both those from American brands to those overseas names that sell their products here. Among those options, one of the most reliable brands to shop from will be Cybex and while we are sure many parents are already familiar with this name, for those who are not yet, they are a German brand with lots of amazing car seats especially those which shine on the trendy and convenient quality.

We have to admit that they are not as affordable as other similar seats like Graco Contender 65 vs My Ride 65 but, when something is more expensive, they tend to have other offerings as well for added value. For parents with young babies, Cybex Eternis S and Sirona M will be two of the most ideal options to consider. Both of them are not only fancy as car seats but also carry some qualities not very often found in car seats prominently made for American market due to mainly sold in European countries.

If what you look at includes a smaller frame, we do think Cybex Eternis S and Sirona M will be nice choices for your vehicle. Being convertible car seats, the best quality of the two will be their ability to be used for a long period of time and for parents who want to save some of the budget to shop for a car seat every few years, these seats will be amazing as well. What’s unique about them is that they have this special feature for added safety which is not present in most car seats.

Cybex Eternis S and Sirona M Design

Car seats are very similar to each other both those from the same manufacturers to across the collection of other brands for chances are they will look like Cybex Eternis S and Sirona M as well. The design of these seats are also identical and as you can see from the sample picture above, both seats are prominently different on the side padding which protect the passenger from impact from the left and right of the vehicle with Sirona M is slightly contoured.

While they are made to be used since early days, we are worried whether smaller babies will fit well using the harness because there is no additional padding here and chances are you will have to use rolled towels or fabric to properly use their harness. As for the fabric however, they are very soft to touch and the padding is adequate for comfort but our favorite part is that you can remove the cover and wash them to keep everything clean for our children.

Cybex Eternis S and Sirona M Installation

Moving further, let’s talk about the installation and in this side, both of Cybex Eternis S and Sirona M are shipped with the lower anchor securing connection as well which you can install easily using the available connector in your seat. However, what many parents find when using the seat in this position is that the anchor is not able to give the tightest installation possible which requires them to modify the reclining position. This issue can be fixed with a lower anchor guide but unfortunately, it is sold separately.

As for the seat belt front facing installation, it is also not the easiest probably because we are not used to the European system and yes, both seats will have a lockoffs feature and this is a bit tricky to learn or even to find. What makes it inconvenient is that unlike regular lockoffs, they have a grippy edge running in one direction so instead of getting the belt tightly before the closing, the seat belt needs to start off loose on the inside of the seat.

Cybex Eternis S and Sirona M Fit

As for the fit, Cybex Eternis S and Sirona M can be utilized since early age, in fact both seats minimum weight limit is the same at 5 lbs. and when tested with a week old baby, it seems there is no problem in fitting which is impressive and the padding inside doesn’t push their neck or head forward as well unlike most car seat inserts. However, if needed, we can still use an extra towel to give the best fit when the lowest harness is still too loose for them.

Fitting across the weight and range are not a problem in both seats but note that for the children who grow up faster on the limb or have long torso then the harness has possibilities to cause discomfort as they are reaching the upper limit which is 65 lbs. What’s different is that Eternis S can be converted into a booster seat as well after the upper harness height no longer conforms to their height while Sirona stops at this point.

Cybex Eternis S and Sirona M Feature

The last point we want to mention is their feature and in this part both Cybex Eternis S and Sirona M have this SensorSafe technology which consists of a receiver that plugs into the vehicle OBDII port and interacts with the chest clip on the car seat. The system will notify when the children are on board and safety notification such as if the chest strap is unbuckled after the car has been driven at least at 5 mph. In addition, there is an app for the technology to alert parents and caregivers with notification and chime.

Cybex Eternis S vs Sirona M

Both of these convertible seats are ideal for parents who want to use one seat for longer but Cybex Eternis S and Sirona M are also different. All of its prominent and main specifications are the same including the weight range of use but, what set them apart is that you can use Eternis S as a booster seat as well when securing the kid with seatbelt and this is useful when their torso or limb are growing faster in which the car seat’s harness no longer fit to their body.

- In-Seat Recline
- Integrated Linear Side Impact Protection System (L.S.P.)
- 3-Position Reclining Headrest
- 10-Position Recline Angle
- 2018 Best of Baby Tech Award Winner for Baby Safety
- 2018 Best Convertible Car Seat - theBUMP Best of Baby Awards
- 2018 "Best in Show" - JPMA Innovation Awards
- Cybex exclusive SensorSafe 2.0 Technology integrated into the 5-point safety harness chest clip, syncs with vehicle receiver and caregiver cellphone to provide alerts to the child's wellbeing


You can go with any of them as they are equally reliable but, we do recommend choosing Cybex Eternis S because not only it has a good fit for smaller babies including infants but it also lasts very long as it can be used in booster mode.