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Radian® 3QXT® FirstClass™ SafePlus™


FirstClass™ Comfort & Ultimate 3-across SafePlus™ Engineering

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Radian® 3QXT® FirstClass™ SafePlus™

Upgrade to award winning FirstClass™ 3-across convertible car seat and travel with ultimate SafePlus™ engineering. Up to 10 years of use without compromise. The Radian® 3QXT®+ FirstClass™ SafePlus™ is shipped with a complimentary Ultra Mat™ in the box, designed to cover the entire vehicle seat to keep car seats firmly installed without causing harm to the upholstery, protecting both car and baby.

This seat has been awarded Best Bet Booster by IIHS.


  • 10 Years 1 Car Seat® - from Birth to Booster (4 - 120 lb) it's all you will need. Grows with your child, ultimate protection on every road trip. 4 modes in 1 seat!
  • SafePlus™ Rear-Facing Engineering up to 50 lb. With 3 modes of newborn protection, our steel anti-rebound bar reduces rebound rotation by up to 50%.
  • Fits 3-Across - our famous slim-fit design with SafePlus™ 6-layer side impact protection with zero compromises to safety, space, or comfort.
  • Mechanically engineered from reinforced automotive grade high-strength steel, our unique core shell shields and protects your child.
  • One hand easy-adjust 12-position headrest, the SafePlus™ completes 6 layers of enhanced, rigorously tested, side impact protection.
  • The original and only all-in-one convertible car seat that folds for travel or compact storage. FAA approved for airline use.

Product Specs

  • Minimum User Weight: 4 lb
  • Maximum User Weight: 120 lb
  • Minimum User Weight - Rear Facing: 4 lb
  • Maximum User Weight - Rear Facing: 50 lb
  • Maximum User Weight - Rear Facing LATCH: 35 lb
  • Minimum User Weight - Forward Facing: 22 lb
  • Maximum User Weight - Forward Facing: 65 lb
  • Maximum User Weight - Forward Facing LATCH: 40 lb
  • Minimum User Weight - Booster: 40 lb
  • Maximum User Weight - Booster: 120 lb
  • Maximum User Height: 57.1 in
  • Product Height: 28.5 in
  • Product Width: 17 in
  • Product Depth: 16 in
  • Product Height - Folded: 28.5 in
  • Product Width - Folded: 17 in
  • Product Depth - Folded: 11.5 in
  • Seat Weight: 34.2 lb
  • Number of Head Support Positions: 12

Care & Maintenance

Covers: Machine wash cold, line dry. Shell and Components: Spot clean

Warranty Information

12 months standard warranty - join lifetime journey care for up to 10 years extended warranty

Car Seat, Product Manual, Safe Stop®, Lap Belt Cushion, Rear-Facing Base, 2 Cup Holders, Harness + Buckle Pads, 2-in-1 Infant Positioning Liner, Newborn Travel High Wedge, Newborn Protection Insert, 2-in-1 Anti-Rebound Panel + Calf Support

We recommend the following Diono® Accessories: Toddler liner, Newborn Harness Pads, Angle Adjuster®, Car Seat Travel Backpack, Side Impact Management Pod, Ultra Matâ„¢, Easy View Mirror®

Yes, you should always read your Radian® 3QXT® product manual and the vehicle's manual that you plan to install it in before use and is sewn into the seat cover. Find more information in our safety hub here.

Your manual is attached to the seat when you open the box. After you have read the manual it must be stored in the storage compartment on the back of the seat. Look for the manual storage icon to locate the manual.

Yes, your Radian® 3QXT® FirstClass™ SafePlus™ is entirely suitable for a newborn. Safest for children rear-facing from 5 lb to 50 lb. It's perfect for newborns with an infant positioning liner and high-riding wedge.

Yes, your Radian® 3QXT® FirstClass™ SafePlus™ is suitable for toddlers. We recommend rear-facing up to 50 lb/forward-facing from 50 lb to 65 lb in the 5-point harness system. Enhance comfort with calf support and toddler liner for luxe travel.

Your Radian® 3QXT® FirstClass™ SafePlus™ is suitable for big kids. Forward-face in 5-point harness to 65 lb, then as a high-back booster up to 120 lb. Enhance comfort with calf support and toddler liner for luxe travel.

When installing your Radian® 3QXT® FirstClass™ SafePlus™ rear-facing in some vehicles the space-saving Angle Adjuster® can make more space available behind the front seat. Check out the video here.

Only use Diono® approved and crash-tested accessories with your Radian® 3QXT® FirstClass™ SafePlus™. The accessories you can use are here.

Diono® is the only car seat manufacturer to offer a folding convertible car seat. This makes it the perfect travel seat as it is so compact and folds into a handy car seat travel backpack. Saving space for trunk or home storage.

51 in is the minimum seat width needed between the vehicle's interior structures to fit your Radian® 3QXT® FirstClass™ SafePlus™. The Radian® fits 3-across in most midsized Sedans up. Learn more here.

Your Radian® 3QXT® FirstClass™ SafePlus™ can be used rear-facing up to 50 lb or 44 in height. We encourage rear-facing as long as possible since it is the safest way for children to travel!

You can use your Radian® 3QXT® FirstClass™ SafePlus™ until 65 lb forward-facing with the 5 point harness and then until 120 lb as a high back booster.

Your Radian® 3QXT® FirstClass™ SafePlus™ uses 30-36 between the vehicle's backseat and front seat back, depending on vehicle's seat shape and contour. Fitting in most vehicles' rear-facing, use our space-saving Angle Adjuster® if more space required.

No. Always follow our guidelines regarding use of items not included with the car seat. We only recommend the use of accessories and spares parts from Diono® as all of these have been tested for use with your Radian® 3QXT® FirstClass™ SafePlus™.

Your Radian® 3QXT® FirstClass™ SafePlus™ comes with two cup holders. They are easy to install through the cup holder slot in the seat cover. Simply insert and twist to lock. Learn more here.

At Diono's Headquarters, a team of engineers continually work on improvements to our car seats. SafePlus™ engineering is the latest advancement in materials and rear and side impact protection, thoroughly tested and built into many of our car seats.

The Radian® 3QXT® FirstClass™ SafePlus™ must be used rear-facing. It works but reducing the rear ward rotation in the event of an accident by up to 50% which protects your child.

The SafePlus™ side impact pod is a safety feature that can be installed on the car seat side closest to the car door. It works by redirecting side impact crash force energy away from the seat and the child.

Our car seat fabrics are tested to ensure they do not contain any legally restricted harmful flame retardants. In order to meet Federal and Canadian Motor Vehicle Safety Standards for flammability, our car seat fabrics do contain flame retardants.

Safety is paramount. Diono® ensures compliance with US Federal Motor Vehicle Safety Standards (FMVSS), US National Highway Traffic Safety Administration (NHTSA), and Canadian Motor Vehicle Safety Standards (CMVSS), regularly testing all car seats.

All Diono® convertible car seats have a life span of 10 years, starting from the date you purchase your seat. In the event the date of purchase cannot be determined then we use the date of manufacture.

Each Radian® is hand built by our manufacturing partners overseen by our highly trained quality control team.

Your Radian is heavy as our engineers will never compromise on the integrity of the famous Diono Steel core. Since launch our reinforced automotive grade high strength steel core is the heart of our Radian, protecting generations of kids everyday.

Your Radian® has a low seat base because as your child grows, they will want to get in and out of your car themselves. This low height makes it very easy for them to get into their seat before you harness them up.

The seat sides on the base expand as your child grows. Parents and Kids really love this feature on the Radian® 3QXT® FirstClass™ SafePlus™ as it makes travel so much easier