Diono does not sell this seat on Amazon. See its own site for photos.

Listed as discontinued

Diono Radian 3RXT All-in-One Convertible Car Seat

An all-in-one car seat with 3 modes: rear-facing harness 5 to 50 lb, 18 to 44 in; forward-facing harness 22 to 65 lb, 30 to 57 in; belt-positioning booster 40 to 120 lb, 40 to 57 in.

At a glance

Fits children from 5 to 120 lb
Up to 57 in tall
3 modes: rear-facing harness, forward-facing harness, belt-positioning booster
10-year usable life
Certified for aircraft use

Not sold on Amazon

Diono lists this seat on its US site. Buy from Diono or an authorized retailer, and confirm the exact model number before you buy.

Diono product page Manual

Specifications checked against Diono’s US site and manual on September 17, 2026. Not hands-on tested. How I research

Who is the Radian 3RXT All-in-One Convertible Car Seat for?

The Radian 3RXT is an all-in-one car seat that Diono's support center dates 2019 to 2023. Its manual lists rear-facing from 5 to 50 lb and 18 to 44 in, a forward-facing harness from 22 to 65 lb and 30 to 57 in, and booster mode from 40 to 120 lb. Do not use it over ten years from purchase.

Reasons to consider it

Rear-facing up to 50 lb or 44 in
A rear-facing top tether connecting strap and a belt locking clip in the parts list
Harness modes certified for aircraft
Diono says it uses 30 to 36 in front-to-back when rear-facing

Things to weigh up

Listed by Diono as a 2019 to 2023 model
Do not use over ten years from the date of purchase
Only the top three harness positions may be used forward-facing
Diono lists the seat at 25.9 lb

My take on the Radian 3RXT All-in-One Convertible Car Seat

The 3RXT matters most to someone who already has one or is considering a used seat, since Diono dates it 2019 to 2023. The purchase date and a complete set of parts and instructions decide whether it can still be used. Its manual lists the same limits as the Radian 3RX, and it starts forward-facing at 22 lb, where the current Radian SafePlus Series manual starts at 26.5 lb.

A research summary of Diono’s published specifications and manual, read October 7, 2026. Not a hands-on test or a crash-safety rating.

Who the Radian 3RXT All-in-One Convertible Car Seat fits

This seat covers 3 stages, and a child has to meet every limit of the stage they are in. Diono gives it a 10-year life from the date of manufacture, so check the date label before using a hand-me-down.

Rear-facing harness5 to 50 lb · 18 to 44 in: The child faces the back of the car, which keeps the head, neck and spine supported in a frontal crash. Keep this mode as long as the child fits it.
Forward-facing harness22 to 65 lb · 30 to 57 in: The child faces forward in the seat’s own harness. Use the top tether every time, and stay in the harness until the child outgrows it.
Belt-positioning booster40 to 120 lb · 40 to 57 in: The seat raises the child so the vehicle’s own lap and shoulder belt sits on the hips and across the shoulder. The child has to sit properly for the whole ride.

A toddler standing next to an empty convertible car seat

What are the Radian 3RXT All-in-One Convertible Car Seat weight, height and age limits?

Diono Radian 3RXT All-in-One Convertible Car Seat limits by mode
Mode	Child weight	Child height	Minimum age	Conditions
Rear-facing harness	5 to 50 lb	18 to 44 in	Not published	LATCH installation limited to 35 lb
Forward-facing harness	22 to 65 lb	30 to 57 in	Not published	22-30 lb must use the middle buckle slot
Belt-positioning booster	40 to 120 lb	40 to 57 in	Not published	—

A child must meet every limit for the mode they use. The labels on your seat and its manual are the final word.

Radian 3RXT All-in-One Convertible Car Seat specifications

Seat weight: Not published
Width: Not published
Usable life: 10 years
Aircraft use: Certified for aircraft (see manual for which modes)

An empty car seat installed on a back seat, seen through an open car door

Will it fit your car?

Diono does not publish a width for this seat, so measure your back seat and compare it with the seat in a store before buying.

Check your vehicle manual for lower anchor positions and any head-restraint rules.
Rear-facing seats need front-seat room: try the install behind the driver before you commit.
Certified for aircraft use, so it can travel as a seat rather than checked baggage.

What to know before you live with it

Installing it rear-facing

Rear-facing covers 5 to 50 lb and 18 to 44 in. LATCH is limited to 35 lb, then the vehicle belt to 50 lb. The manual says to always use the detachable rear-facing base rear-facing: align the arrows, slide it back and press the metal lever to lock it. Do not use the adjustable bottom rear-facing. The recline level indicator shows infant use from 5 to 22 lb and toddler use from 40 lb. The rear-facing top tether connecting strap wraps around a seat track bolted to the vehicle frame, and the manual limits it to rear-facing installs. The seat should move less than 1 in at the belt path.

Source: Diono Radian 3RXT manual (PDF)

Forward-facing rules

The forward-facing harness covers 22 to 65 lb and 30 to 57 in, but the manual says not to turn a child forward until at least one year old and 22 lb, and Diono recommends rear-facing until at least two. Always use the top tether. Only the top three harness positions are allowed forward-facing. Lower the adjustable bottom if the child is over 25 lb. The SafeStop is for 22 to 40 lb and comes off at 40 lb. LATCH goes to 40 lb, then the lap/shoulder belt to 65 lb. Children from 22 to 30 lb use the middle buckle slot.

Source: Diono Radian 3RXT manual (PDF)

Booster mode, headrest and care

Booster mode covers 40 to 120 lb and 40 to 57 in. The 5-point harness must be removed, and only the vehicle lap/shoulder belt is used, with the lap portion under the side nubs. Check that the belt retracts before each use. The headrest can be used at its lowest position once the child fits the third harness slot; to move it, unfasten the fabric panels, tilt the top toward you and slide it. Remove the seat pad foam and infant support wedge before washing. Fabrics go in cold water on a gentle cycle and dry flat in the shade.

Source: Diono Radian 3RXT manual (PDF)

Is the Radian 3RXT All-in-One Convertible Car Seat recalled?

17C003000: does not cover this model. The Part 573 report for campaign 17C003000 lists six models only: Radian R100 (model no. 16600 or 16000), Radian R120 (16800 or 16000), Radian RXT (16900 or 16000), Olympia (30100), Pacifica (30400 or 300000) and Rainier (30300 or 300000), built between November 25, 2013 and September 5, 2017. The Radian 3RXT is a separately named Radian 3 series seat and is not among the listed models. Campaign source (read October 7, 2026).

Each campaign naming this family was read against this model’s numbers and build dates, and none covers it. Still check your seat’s model number and date of manufacture before use, especially on a used seat.

NHTSA recall search · Recent car seat recalls

Radian 3RXT All-in-One Convertible Car Seat: common questions

What are the Radian 3RXT weight and height limits?

Rear-facing is 5 to 50 lb and 18 to 44 in, the forward-facing harness is 22 to 65 lb and 30 to 57 in, and booster mode is 40 to 120 lb and 40 to 57 in.

Diono Radian 3RXT manual (PDF) (opens in a new tab)

Does the Radian 3RXT expire?

Yes. The manual says not to use it once it is over ten years from the date of purchase, or if any part is damaged, broken or missing.

Diono Radian 3RXT manual (PDF) (opens in a new tab)

Can the Radian 3RXT go on a plane?

In harness mode, yes. The manual's aircraft steps use the lap belt instructions for rear-facing or forward-facing, and for rear-facing it says to ask the flight attendant for a seat belt extender. Booster mode is not certified for aircraft.

Diono Radian 3RXT manual (PDF) (opens in a new tab)

How does the 3RXT compare with the Radian 3RXT SafePlus?

The 3RXT manual starts rear-facing at 5 lb and forward-facing at 22 lb. The 3RXT SafePlus is listed with rear-facing from 4 to 50 lb and the forward-facing harness from 26.5 to 65 lb. Both list booster mode at 40 to 120 lb.

Diono support: Radian 3RXT SafePlus (opens in a new tab)

What is the rear-facing top tether strap on the 3RXT for?

It is a connecting strap that wraps around a vehicle seat track bolted to the frame, giving the top tether hook a D ring anchor. The manual says to use it only in rear-facing installs and to check the vehicle owner's manual for anchor points.

Diono Radian 3RXT manual (PDF) (opens in a new tab)

How wide is the Radian 3RXT?

Diono lists it at 17 in wide, 16 in deep and 28.5 in tall, with a seat weight of 25.9 lb.

Diono support: How wide is the Radian 3RXT (opens in a new tab)

Answers refer to the model and manual version on this page. Check the instructions supplied with your seat.

Before you buy

Weigh and measure your child. The limits above are the manufacturer’s, and a child has to meet all of them for the mode they will use.
Confirm the exact version. Colors, retail exclusives and model numbers change limits more often than you would expect.
Read the manual before you buy, not after. It is linked above and holds the fit rules, the install methods and the expiry.
Check recalls by model number and date of manufacture, and register the seat with Diono so you hear about the next one.

Sources

Other Diono convertible car seats

Model	Top child weight	Seat weight	Width	Usable life
Radian 3RXT All-in-One Convertible Car Seat (this seat)	120 lb	—	—	10 years
Radian 3QX SafePlus All-in-One Convertible Car Seat	120 lb	—	—	10 years
Radian 3QXT SafePlus All-in-One Convertible Car Seat	120 lb	—	—	10 years
Radian 3QXT FirstClass SafePlus (Radian 3QXT+) All-in-One Convertible Car Seat	120 lb	—	—	10 years
Radian 3R SafePlus All-in-One Convertible Car Seat	120 lb	—	—	10 years
Radian 3RXT SafePlus All-in-One Convertible Car Seat	120 lb	—	—	10 years
Radian 3RXT SafePlus Max All-in-One Convertible Car Seat	120 lb	—	—	10 years
Radian 3R All-in-One Convertible Car Seat	120 lb	—	—	10 years
Radian 3RX All-in-One Convertible Car Seat	120 lb	—	—	10 years