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Diono Radian 3QXT Ultimate 3-Across All-in-One Convertible Car Seat

$ 399.99 USD

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The ultimate 3 across All-in-One car seat from birth to booster (4 - 120 lb / 1.8 - 54 kg).  Featuring 4 stages of complete newborn protection and all new Diono Safe+TM engineering to provide the next generation in car seat safety.

What’s new for 3QXT?

  • Suitable from 4 lb / 1.8 kg
  • Extended rear facing up to 50 lb / 22.7 kg
  • Easy remove covers - machine wash and dry
  • Improved rear-facing recline
  • Comfort+ memory foam cushion for improved seat base comfort
  • easy adjust 12 position headrest with 22% increase in occupancy space from
  • headrest - with built in side impact protection
  • side impact protection with extended sidewalls
  • steel anti-rebound bar
  • 2-in-1 infant positioning liner
  • anti-slip harness pads
  • newborn travel high wedge for optimum newborn positioning roll-over tested
  • side impact tested
  • rear impact tested
  • tested using 2x impact force required by US FMVSS 213
  • side impact management pod
  • newborn harness pads
  • newborn protection insert
  • Improved headrest design made with high performance foam padding for child comfort
  • Premium soft fabrics and detailing
  • Latch and rear facing tether storage
  • Instruction manual storage
  • Improved seat base design with expandable seat width
  • Easy-access side storage for harness cleaning/replacement

What makes radian® 3QXT great?


Features Safe+TM newborn travel high wedge, Safe+TM newborn protection insert, Safe+TM 2-in-1 infant positioning liner and Safe+ newborn harness pads to provide a custom fit from birth.

  • Creates near lie-flat travel position for newborns while reducing head slump and keeping airways open. Simply remove as baby grows.
  • Made from energy absorbing materials to support and protect. Super soft padding for extra newborn comfort. Simply remove as baby grows.
  • 3. SAFE+ 2 IN 1 INFANT POSITIONING LINER Gives extra infant comfort and toddler body support. Simply remove as baby grows. from rebounding or “bouncing back” into
  • 4. SAFE+ NEWBORN HARNESS PADS Small sized newborn harness pads for added safety and comfort.

Radian® 3QXT is subjected to a combination of the most rigorous crash tests; front, rear, and side impacts, and rollover test to make sure we have the safest seat possible.

With 5 ways to travel from birth to booster, the radian® 3QXT adapts as your child grows to offer a custom fit from birth to 120 lb.

Designed and engineered with all new Diono Safe+TM protection. Now you can keep your child rear facing for even longer up to 50 lb (approx. 4 years old).

Built with our famous radian slim fit design, to fit 3 across in most vehicles without compromising child or passenger comfort.

Designed and engineered following the latest European research and technology in crash energy management. The pod is placed on the side of the car seat facing the door and is engineered to channel energy around the back of the car seat and away from the child in the event of a side impact.

Featuring 8 layers of Safe+ side impact protection (with Safe+ Side Impact Management Pod included.) Engineered with interlocking EPS & EPP foam, high density plastic and steel reinforcement to create ultimate side impact protection, without compromising 3 across fit in most midsize vehicles.

One click connection to the seat base and fits against the vehicle back seat. The Safe+ steel anti-rebound bar prevents the seat from rebounding or "bouncing back" into the vehicle seat. Reduces rebound rotation by up to 50%.

All new upgraded mechanically engineered, reinforced steel core. Made from automotive grade high strength steel to shield and protect. Manages and dissipates energy.

Contoured and engineered with the latest European side impact research and technology in crash energy management. Features 22% increase in headrest range from the Radian R series with built in side impact protection to improve child head containment in the event of a collision.

The only All-in-One car seat that folds for easy travel and transport, FAA approved and aircraft certified.

Overall Age/Weight Range

Suitable from 4 - 120 lb / 1.8 - 54 kg

Rear Facing (RF) convertible weight limit

4 – 50 lb / 1.8 – 22.7 kg

Forward Facing (FF) convertible weight limit

22 – 65 lb / 10 – 29.5 kg

Belt Positioning Booster (BPB) Mode weight limit

40 – 120 lb / 18 – 54 kg

Belt Positioning Booster (BPB) Mode height limit

57" / 145 cm 

Seat Weight

25.8 lb / 11.7 kg

Overall seat dimensions (lowest position inches)

H 28" x W 17" x D 16"

Overall seat dimensions (lowest position cm)

H 71cm x W 44cm x D 41cm

Overall seat dimensions (highest position inches)

H 31" x W 17" x 16"

Overall seat dimensions (highest position inches)

H 80cm x W 44cm x D 41cm

Vehicle seat bite to front FF length

17” / 44cm

Inside shoulder width

12” / 31cm

Inside hip width

12” / 31cm

Inside seat depth

13” / 33cm

Rear facing installation depth

30”/ 76.2cm

Inside seat height
(base to accommodating)

26” / 67cm

External widest point (without Safe+ Side Impact Management Pod)

17” / 44cm

We are happy to accept returns on unused, unaltered merchandise in its original packaging and with all original tags. Return requests must be made within 7 days from the original date of purchase for a refund (less any shipping fees) and within 30 days for store credit or exchange. All returns must be pre-authorized by a Tadpole staff member, either in person, or by phone or email if you are mailing the merchandise back. Damaged packaging will be subject to a 10% restocking fee. All unaltered merchandise could also be subject to a restocking fee anywhere between 10-25% depending on the value of the original merchandise and the reason for return. Once we have received your return we will process the refund/store credit/exchange within 2 business days. Store credit expires after 6 months. 

The following items are final sale i.e. NON-REFUNDABLE:

  • All special orders and sale items; all furniture sales are final sale; damaged, defective, or missing furniture pieces will be replaced.
  • All stroller and car seats sales are final; damaged merchandise will be covered under the manufacturer's warranty.
  • All opened breastfeeding products, opened feeding products, body products are final sale.
  • All pantry items are final sale. 
  • Gift cards are non-refundable. 
  • Gifts can only be exchanged or offered store credit if returned within 30 days of the original date of purchase. 

Please note:

Orders that qualify for free shipping may be subject to a restocking fee.

If an item is damaged once opened, or during shipping, please notify us immediately. We will gladly accept returns of defective merchandise within 7 days of purchase/receipt of goods. Returned items are your responsibility until they reach the return address. Please ensure your package is returned securely to prevent any damage to the item or its packaging. Tracking is highly recommended. Any returns that are damaged when we receive them will not be refunded. We are not responsible for any items that are returned to us in error. 

Credit card orders will receive refunds in the form of a credit to the card. Please allow at least one billing cycle for credit to appear on your statement.

To request a return via email, send an e-mail to with your name, address, invoice number, item you are returning, and why you are returning it. 

Important: Please note that we do not refund delivery fees or original shipping charges.

Please send returns to:
Attn: Returns
58 Clarendon Street
Boston, MA 02116