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Radian® 3RX


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Radian® 3RX

The Diono Radian® 3RX is the original slim fit 3 across all-in-one convertible car seat, designed to protect from birth to booster seat (5 - 120 lb). Featuring 12 position adjustable head support, extended rear-facing up to 50 lb and steel reinforced frame, expect 10 years of safety from just one car seat


  • 12 POSITION HEADREST - Creates a safe and comfortable fit for rear facing, forward facing and booster seat modes
  • INFANT HEAD SUPPORT LINER - Features padded support for added comfort. Simply remove as your infant transitions from rear-facing to forward facing booster seat
  • 10 YEARS ONE CAR SEAT - From rear-facing to forward facing Radian 3RX adapts as your child grows from birth to booster. Suitable from 5 - 120 lb
  • REAR FACING FOR LONGER - Designed and engineered to keep your child rear-facing for as long as possible up to 50 lb
  • STEEL REINFORCED FRAME - Mechanically engineered, reinforced steel core, made from automotive grade high strength steel to shield and protect
  • THE ORIGINAL RADIAN 3 ACROSS - Built with our famous Radian slim fit convertible design for a 3-across option only with Diono Radian® combinations without compromising child or passenger comfort. Feel safe having your children secure in the backseat

Product Specs

  • *Minimum User Weight: 5 lb
  • *Maximum User Weight: 120 lb
  • *Minimum User Weight - Rear Facing: 5 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
  • *Seat Weight: 28.1 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 - extended to 36 months when you register with Diono® post purchase

Radian® 3RX® Car Seat, Instruction Manual, SafeStop, Cup Holder, Infant Support, Harness Pads, Rear Facing Base, Lap Belt Cushion, Rear-Facing Top Tether Strap

Radian® R series manuals are located in a pouch sewn into the seat cover on the back of the seat. All Radian® Q series manuals are located in the storage compartment on the back of the seat. Look for the manual storage icon to locate the manual.

The Radian® Angle Adjuster is an accessory which can be purchased separately.

On all Radian® models including R-series and Q-series, the harness should be placed at or just below the child's shoulder when they are rear-facing. The harness should be snug. You should not be able to pinch the webbing at your child's shoulders.

Use of the harness pads are optional on seats made as of 2018 and forward. For seats made prior to 2018, their use is required when using the seat forward-facing, but still optional rear-facing.

The handle is only used to adjust the height of the head support. It does not adjust the height of the harness straps.

Yes, a removable cup holder is included in the box with your Radian® 3QX, 3QXT®, 3QXT® FirstClass™ SafePlus™, 3RX, 3RXT®, and the 3RXT® SafePlus™ car seat. Cup holders can be easily installed by inserting the stem into the cup holder slot.

Rebound bars are not sold separately. They can't be used in a Diono seat that doesn't originally have one. Rebound bars are sold to customers with missing or damaged part. If you need a spare rebound bar, contact Diono customer service for help.

The bottom of the Radian® 3R and 3Q series do fold for more compact storage.

51 inches (129.5 cm) is the minimum vehicle seat width needed between door handles (or other vehicle interior structures) to fit 3 Radian® models.

The rear-facing base is included with all of our Radian® all-in-one convertible car seats.

Yes, anytime a Diono seat is installed rear facing the rear facing base must be installed.

The adjustable bottom should be lowered when the occupant is forward facing while using the 5-point harness system and weighs 25 lb or more. The seat bottom should not be lowered while in rear-facing or booster mode.

When in rear-facing, the detachable base creates the correct recline angle.

A rear-facing child is too tall for the seat if any of the following are true: they are 44in or taller, there is 1 1/2in or less between the top of their head and the top of the seat shell.

All Diono All-in-One car seats can be used rear-facing up to 50 lbs or 44 inches height. We encourage rear-facing as long as possible, since it is the safest way for children to travel!

A rear facing Radian® uses 30-36 inches (76 - 91.4 cm) between the vehicle's backseat and seat back of the front seat. This also depends on the vehicle's seat shape and contour.

When in forward-facing mode a child is too tall for the seat if they are 57in or taller, the tops of their ears are higher than the seat shell, or their shoulders are touching the bottom of the adjustable head support at its highest position.

Both installations are safe and have been approved for forward-facing installations. Neither is safer than the other, use the one that gives the best installation.

Both installations are safe and have been approved for rear-facing installations. Neither is safer than the other, use the one that gives the best installation.

Diono seats have not been tested with harnessing systems that are not included with the car seat. Do not use any 3rd party or after market harness system with your Diono car seat.

No. Always follow the car seat manufacturer guidelines regarding use of items not included with the car seat.

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.

No. Thick clothing creates extra space between the harness and the child which is a safety hazard. We recommend removing the coat and harnessing your child in their seat. Then you can place their coat on backwards or use a blanket to keep them warm.

Diono car seats and boosters are tested to meet or exceed Federal Motor Vehicle Safety Standards (FMVSS) per NHTSA, and Canadian Motor Vehicle Safety Standards (CMVSS), per Transport Canada.

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.

Please consult the seat manual. Diono car seats manufactured in 2017 & prior will continue to be approved for use with Ford's inflatable seat belts. Newer seats will not allow them to be used and will be stated in the car seat's manual.