Eternis S

The CYBEX Eternis S is the only seat your child will need from birth and beyond. With three modes - rear-facing, forward-facing, and booster, this All-In-One Convertible Car Seat is designed for use from birth up to 120 lbs.
  • Age 0 - 10 yrs
  • Height 57"
  • 4 - 120 lbs.
Comfort: Pepper Black

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32 in
19.8 in
25.5 in
26 lbs

25.3 in
19.8 in
25.5 in
26 lbs

What is included?

What is included?

  • Eternis S Toddler Car Seat
  • Newborn Inlay
  • Cup Holder
  • User Guide



Where can I get replacement parts for my product?

You can order replacement parts from our customer service team at ParentLink. Please contact them at or by calling 1-877-242-5676.

Does this seat have a cupholder?

Yes this seat comes with 1 cupholder. An additional cupholder may be available to purchase as an accessory. If not available as an accessory, contact ParentLink for spare part information at or by calling 1-877-242-5676.

Installation and Securing your child

Can my child sit in the car seat in a forward-facing position?

The American Academy of Pediatrics and the National Highway Traffic Safety Administration recommend that children ride rear-facing as long as possible, until they outgrow the height or weight limits of their rear-facing car seat. This CYBEX infant car seat is designed to be used ONLY in the rear-facing position and may never be used forward-facing in a vehicle.

Can I also use this seat without the base?

This is a multi-mode car seat and does not feature a detachable base

Where can I check to make sure my car seat is installed properly?

CYBEX recommends getting your car seat installation checked by a Certified Child Passenger Safety Technician. At CYBEX we have certified car seat technicians available to assist you though our customer service team at ParentLink at 1-877-242-5646 or We also have virtual appointments available at

Is it safer to use lower anchors or the vehicle's seat belt?

The safest installation method is the one that allows you to install the car seat correctly. Either method, if used in accordance with the car seat owner's manual and vehicle's owner’s manual requirements, provides protection. The car seat has been tested to meet safety standards installed by either method. Most car seats have lower anchor weight limitations, so please refer to your car seat owner's manual for those specific limitations.

Why is it important to use the tether for forward facing installation?

The use of a tether can reduce the risk of injury by reducing movement of the car seat and the child in certain kinds of crashes. The tether should be used whenever possible for forward-facing installations with either the lower anchors or seat belt. For proper installation, please refer to both the child safety seat manual as well as the vehicle’s owner manual.

How do I know if I have LATCH available in my vehicle to install the car seat?

Most U.S. vehicles manufactured on or after September 1, 2002, are equipped with LATCH. Refer to your vehicle owner’s manual under the Child Restraints section to confirm and see where your latch connections are.

What is the difference between Rigid Latch vs Flexible Latch?

Flexible lower anchor connectors are connected to each other with flexible webbing. Rigid lower anchor connectors are rigidly attached to the car seat shell or car seat base and there is no flexible webbing. Rigid lower anchor connectors are spaced exactly 11 inches apart to correspond with the standard spacing of lower anchors in the vehicle. CYBEX allows flexible lower anchors to be used with spacing between 11 - 20" apart and given the vehicle manufacturer allows this use.

Safe Travel

What kind of clothing should my child wear when seated in the car seat?

Thick clothing prevents the harness from lying snugly against the body. This incorrect harness use results in a loose or slack harness which in turn reduces the performance of the child restraint in crashes. Also, in everyday use, the loose harness could result in the harness slipping off the child's shoulders. For this reason, your child should wear everyday clothing. Thick clothing, such as puffy jackets, should not be worn in the car seat. In cold weather, after your child has been harnessed in the car seat, their jacket or a blanket can be placed over the child for extra warmth.

Can I use this seat on a flight?

Yes, this seat is approved for use on an airplane according to the requirments of the Federal Aviation Administration (FAA). The FAA recommends that you secure your child for air travel in an appropriate Child Restraint based on your child's weight and size. Turbulence can happen with little or no warning. When turbulence occurs, the safest place for your child is in a properly installed Child Restraint instead of in an adult's lap or on the aircraft seat with its seat belt. Keeping your child in a Child Restraint during the flight will help ensure your family arrives safely at your destination. Please contact your airline before departure to make sure this restraint meets their requirements. Always refer to your Child Restraint owner's manual for aircraft installation.


Can the car seat be used in a seating position that has a side airbag?

Yes, the car seat can be used in the seating position adjacent to a side airbag unless otherwise indicated in the vehicle owner's manual.

When does my CYBEX S Eternis S seat expire?

You can find the date of manufacture and expiration date on a sticker located on the bottom of your CYBEX Eternis S. Every car seat has an expiration due largely to allow you the benefit of regulatory changes and technology enhancements in child passenger safety. The Eternis S has been certified for 10 years from the date of manufacture. Once your car seat has reached its expiration date, we recommend recycling the seat by contacting your local community recycling center.

Is it ok to keep using my CYBEX car seat after an accident?

We at CYBEX always recommend that you replace child restraint after a crash of any kind, even if it was unoccupied. A crash can cause unseen damage to the child restraint that may not be visible and this damage can pose an increased risk to safety. Your insurance company may be able to provide some assistance in replacing the child restraint. For more info, please reach out to our Customer Service team at ParentLink at or by calling 1-877-242-5676.

When is a child too big for the Eternis S car seat?

The Eternis S car seat is designed for children from 4-50 lbs. and up to 48" tall. In addition, you will want to ensure that the top of the child's head is a minimum of 1 inch below the top of the child restraint for rear-facing use. This allows for proper protection in the event of a crash. We recommend you keep your child rear-facing in a convertible or all-in-one seat as long as the seat allows, according to the manufacturer's specifications, before turning them around to ride forward-facing. For this seat that would be 4-50 lbs. for rear-facing, 22 -65 lbs. forward facing, and 40-120 lbs. in booster mode. Please refer to your owner's manual for latch, tether, harness, and recline limitations in each seating position.

How long should I keep my child rear facing for?

The head of a young child is large and heavy in proportion to the rest of their body and their neck is relatively weak. A rear-facing child restraint supports the head, neck, and spine, and therefore may help reduce the risk of serious injury. We recommend keeping your child rear facing in a properly installed car seat as long as possible, until they reach the highest weight or maximum height allowed by the seat in the rear-facing position.

Can I used a rolled towel or pool noodle under the base of my car seat to achieve the correct recline angle?

In some vehicles, even when your car seat is in the most reclined position, it may be necessary to place a rolled towel or pool noodle beneath (not behind) the car seat near the vehicle seat back to provide enough recline so that the recline indicator is in the correct zone for rear-facing use. For an infant car seat with the base, the adjustable foot should be stored before adding the rolled towel or pool noodle. For a convertible or all-in-one car seat, make sure the car seat is set in an appropriate rear-facing recline position, and then add the rolled towel or pool noodle. For additional details, please refer to your product instructions or contact our ParentLink customer service team.   


Are both linear side-impact protectors (L.S.P.s) needed?

The Linear Side-impact Protection (L.S.P.) reduces the forces of a side-impact collision and thus also the risk of injury. For an active L.S.P. you ONLY deploy the L.S.P. towards the vehicle door. You never deploy it towards the center of the vehicle. Also, do not use the L.S.P. when installing the car seat in the middle seat of the vehicle. The only exception to a middle seat installation are boosters where the L.S.P. is in a static or fixed position on the side wings or on an infant seat shell and you don't have to do anything to deploy them.