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Radian® 3-across

Radian® 3-across

The original all-in-one convertible car seat since 2006

Radian® was born when our expert team recognized the need for a better way to prepare for your growing family and busy back seats while keeping your very important passenger as safe as possible.

The original 3-across Radian® features a slimline, space-saving design at only 17” wide that allows you to install three across in most mid to large-sized vehicles in a variety of configurations from rear-facing to forward-facing with harness, fitting 3-across each and every time.

Engineered with the famous diono® full steel core for maximum safety. This high-strength core has inherent integrity and forms an unyielding structure to shield and protect your child. We didn’t stop there; our aluminum-reinforced sides and thick energy-absorbing foam distribute crash forces to guard your child’s vulnerable side and head, which is critical in side-on collisions.


By Kimberly Gross

Let me explain why my husband and I like the 3QXT so much: 1) This carseat is rock solid. That gives us a lot of confidence in its stability and also its capability to absorb crash forces. The steel frame just seems more sturdy than other products we considered. 2) Despite its robustness, the 3QXT is actually less bulky than other similar seats we looked at, which allows us to fit 3 across the back seat—an important feature when you have 3 boys under 5 years old like us! It almost seems as though the engineers used every inch of the seat in the most efficient manner to save on space.

This is a sturdy, nice and safe car seat.


By Anthony Young

Bought the purple one for our daughter due in July and will be baby number three. Until then, it’s been being “tested” by our 2yr old son. Purchased it because we already had two car seats from another brand and needed to ensure the third car seat was slim enough to fit in the back. Fits perfectly. It’s HEAVY, but well built. I can’t wait to use the newborn insert. Highly recommend the car seat. I wish I started with this brand for my first child.

Well built and gives peace of mind.


By Eileen

We use Diono Radians for all our kids because of the narrow three across feature. The kids are safe and secure back there! They like them too-- which is awesome because none of them liked the infant bucket seat before they graduated to Radians!


By Joseph Casares

Saved all 3 of my children’s lives in a roll over accident everyone came out without a scratch. The police even said normally kids and most adults don’t survive rollovers like ours where we went over a retaining wall and a guard rail. The police said it was the car seats that saved the kids.

Shop the 3 across family

Radian® 3QXT® FirstClass™ SafePlus™

FirstClass™ Comfort & Ultimate 3-across SafePlus™ Engineering


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Radian® 3QXT® SafePlus™

4-stage newborn safety & 3-across: the advanced all-in-one convertible


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Radian® 3QX SafePlus™

3-stage newborn safety & 3-across: the advanced all-in-one convertible


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Radian® 3RXT® SafePlus™

Our best selling 3-across all-in-one convertible car seat with SafePlus™ engineering


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Radian® 3R® SafePlus™

The original 3-across all-in-one convertible car seat with SafePlus™ engineering


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Radian® 3R®

The original 3-across all-in-one convertible car seat


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Find the right car seat for you

Radian® 3QXT+

The luxury 3 across All-in-One Car Seat for first-class travel from birth to booster.

  • MSRP - $649.99
  • Advanced 4-in-1 newborn protection
  • SafePlus™ 2-in-1 anti-rebound panel and adjustable calf support
  • Exclusive premium fashion
  • Includes Ultra Mat Seat protector & 2 XL Cup Holders
  • SafePlus™ Engineering
  • 8 layers of SafePlus™ side impact protection
  • SafePlus™ side impact management pod
  • SafePlus™ newborn protection insert
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Radian® 3RXT

The original 3 across All-in-One convertible car seat.

  • MSRP - $449.99
  • Award winning Radian All-in-One Convertible Car Seat
  • Rear-facing for longer
  • Slim fit design for 3 across
  • One hand easy adjust 12 position headrest
  • Steel reinforced frame
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Radian® 3RX

Slim fit 3 across all-in-one convertible car seat.

  • MSRP - $379.99
  • 12 position headrest
  • Infant head support liner
  • 10 years one car seat
  • Slim fit 3 across
  • Rear-facing for longer
  • Steel reinforced frame
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Radian® Accessories

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