Britax Roundabout 55 Convertible Car Seat, Onyx


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The BRITAX ROUNDABOUT? 55 convertible car seat is designed for children rear facing from 5 to 40 pounds and forward facing from 1 year and 20 lbs up to 55 pounds. The ROUNDABOUT 55 achieves revolutionary head safety through the use of BRITAX SafeCellTM Technology, Integrated Steel Bars, and Versa-Tether? that work together to minimize head excursion and reduce the risk of head injury during a frontal impact. The ROUNDABOUT 55 also incorporates BRITAX Side Impact Protection, offers a five-point harness, and multiple buckle and recline adjustments. A body pillow is provided for comfort. Features Benefits: 360 Degree Protection Features SafeCell? Technology features SafeCells designed to compress in a crash, significantly lowering the center of gravity and counteracting the forward rotation of the child seat which normally propels the child toward the front seat Integrated Steel Bars strengthen the connection to the vehicle and reduce forward flexing of the child seat during a crash Patented, Energy-Absorbing Versa-Tether? features a staged-release tether webbing to slow the forward movement, reducing the crash forces reaching the child, and a two-point attachment to minimize forward rotation while anchoring the top of the child seat Side Impact Protection comprised of deep side walls lined with energy-absorbing EPP foam distributes crash forces, shields from vehicle intrusion, and contains the head, neck and body Tangle-Free, Five-Point Harness distributes crash forces across the strongest parts of the body and provides a secure fit Superior Fit and Comfort Features 55-pound Weight Capacity for safety and comfort as your child grows Rear and Forward Facing Recline for child comfort and positioning High Density Comfort Foam provides an extra layer of padding to gently cushion your child Two Buckle Positions for your growing childInfant Positioning Insert may be necessary for small infants to achieve a snug fit of the harness around your child (sold separaThe BRITAX ROUNDABOUT 55 Convertible Car Seat achieves optimum head safety through the combination of BRITAX SafeCell Technology, integrated steel bars, and a Versa-Tether, which work together to minimize head excursion and reduce the risk of head injury during a frontal impact. The seat fits children in the rear-facing position weighing from 5 to 40 pounds, and children in the forward-facing position starting at one year old and 20 pounds, up to 55 pounds.

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ROUNDABOUT 55 (Onyx)
Convertible Car Seat

At a Glance:

  • Age/Weight Requirements: In rear-
    facing position, fits children weighing 5 – 40 pounds; in forward-facing position, fits children 1+ years old weighing 20 – 55 pounds

  • Warranty: 1-year
    limited warranty
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Britax Roundabout 55 Convertible Car Seat


Available in (from left to right):
Onyx, Davenport, and Smokey Pearl.

Britax Roundabout 55 Convertible Car Seat
Safety features include SafeCell Technology and True Side Impact Protection.
View larger.
Britax Roundabout 55 Convertible Car Seat
Comfort features include dual recline positions and high-density comfort foam.
(Shown here in Davenport.) View larger.

BRITAX 360 Degree Protection
The BRITAX ROUNDABOUT 55 features technologies that work to minimize injury to your child during a crash from any direction, including both frontal and side impact crashes – the most frequent types of crashes. These technologies work together with other features on the car seat to minimize injury to your child during a crash by:

  • keeping your child in the vehicle,
  • diverting crash forces away from your child,
  • helping to slow down your child’s body,
  • minimizing movement of your child, and
  • protecting your child’s brain and spinal cord.

SafeCell Technology for Advanced Head Safety
Designed with SafeCell Technology, the ROUNDABOUT 55 features SafeCells, which are engineered structures located in the base of the seat designed to compress in the event of a crash. This compression significantly lowers the center of gravity and counteracts the forward rotation of the car seat, delivering unprecedented performance in a crash.

The ROUNDABOUT 55 also features integrated steel bars, which strengthen the connection to the vehicle and reduce the forward flexing of the car seat. In addition, the energy-absorbing Versa-Tether anchors the top of the car seat and minimizes forward rotation to reduce the crash forces that can reach your child if an accident occurs. These three features work together as a system to provide revolutionary head safety protection for your child.

Side Impact Protection for Added Security
To keep your child safe in the event of a side-impact collision, the ROUNDABOUT 55 includes Side Impact Protection. Side Impact Protection is a system composed of a rigid seat shell with deep side walls and energy-absorbing EPP (Expanded Polypropylene) foam lining the shell. These combined features work together to protect your child’s head and chest from incoming side-impact crash forces by distributing the forces over a larger surface area, helping shield your child from vehicle intrusion and contain your child’s head and body in the seat.

Premium Fit and Comfort Features
Whether children are watching the world go by or snuggling in for a nap, they’ll enjoy that the ROUNDABOUT 55 reclines in both the forward and rear positions. And thanks to additional features, which include high-density comfort foam and a plush cover set with a matching belly pad, they’ll always ride in style and comfort. A 55-pound weight capacity, two buckle positions, and a tangle-free five-point harness with four harness-height settings ensure that your growing child will ride safely and comfortably. Plus, an optional Infant Positioning Insert (sold separately) allows you to properly and snugly fit smaller infants into the car seat.

Ease-of-Use for Safety and Convenience
Packed with perks for parents, the ROUNDABOUT 55 makes it easy to secure your child in the proper position without guesswork. Premium lower LATCH connectors make for a quick, simple, and tight installation, while the push-button allows you to easily uninstall the connectors. Easy-to-access built-in lock-offs allow you to install the car seat with ease using your vehicle’s lap and shoulder belt.

Additionally, an anti-slip contoured base grips and protects the vehicle seat, ensuring a tight installation in all types of vehicles. Convenient holders keep harness straps out of the way when you’re placing your child in the seat.

The BRITAX ROUNDABOUT 55 Convertible Car Seat is backed by a one-year limited warranty.

What’s in the Box
One BRITAX ROUNDABOUT 55 Convertible Car Seat and manual.


  • The Britax Roundabout 55 convertible car seat is designed for children rear facing from 5 to 40 pounds and forward facing up to 55 pounds
  • Safecell technology features safecells designed to compress in a crash, significantly lowering the center of gravity and counteracting the forward rotation of the child seat which normally propels child toward the front seat
  • Integrated Steel Bars strengthen the connection to the vehicle and reduce forward flexing of the child seat during a crash
  • Side Impact Protection comprised of deep side walls lined with energy-absorbing EPP foam distributes crash forces, shields from vehicle intrusion and contains the head, neck and body

Britax Roundabout 55 Convertible Car Seat, Onyx

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