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

Diono Radian 3QXT SafePlus All-in-One Convertible Car Seat

An all-in-one car seat with 3 modes: rear-facing harness 4 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 4 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 3QXT SafePlus All-in-One Convertible Car Seat for?

The Radian 3QXT SafePlus is an all-in-one car seat: rear-facing from 4 to 50 lb and 18 to 44 in, forward-facing with the harness from 22 to 65 lb and 30 to 57 in, then a booster from 40 to 120 lb. It adds a Side Impact Management pod and newborn insert, and expires 10 years after purchase.

Reasons to consider it

A Side Impact Management pod that clips onto the side next to the door
A newborn protection insert for 4 to 10 lb, used with the infant support cushion
Rear-facing to 50 lb or 44 in with a detachable base and an anti-rebound bar
A 17 in width that folds to 11.5 in deep, per Diono

Things to weigh up

Diono lists the seat at 32 lb
LATCH is limited to 35 lb rear-facing and 40 lb forward-facing
The 10-year life is split: 8 years in the 5-point harness and 2 years as a booster
The newborn protection insert must never be used without the infant support cushion

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

The 3QXT suits a family that wants the 3QX's narrow all-in-one shell plus the newborn protection insert, newborn harness pads and a Side Impact Management pod for the door side. Diono lists it at 32 lb, which matters if it will move between cars. The 3QX keeps the anti-rebound bar but drops those extras and is listed at 31.3 lb; the 3QXT FirstClass swaps the bar for an anti-rebound panel and adds a toddler liner.

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 3QXT SafePlus 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 harness4 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 3QXT SafePlus All-in-One Convertible Car Seat weight, height and age limits?

Diono Radian 3QXT SafePlus All-in-One Convertible Car Seat limits by mode
Mode	Child weight	Child height	Minimum age	Conditions
Rear-facing harness	4 to 50 lb	18 to 44 in	Not published	—
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 3QXT SafePlus All-in-One Convertible Car Seat specifications

Seat weight: Not published
Width: Not published
Usable life: 10 yearsTen years from date of purchase (8 years in 5-point harness, 2 years in booster)
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

What the 3QXT adds

The shared manual marks three items as included with the 3QXT and 3QXT FirstClass only. The Side Impact Management pod hooks into slots on the side and back of the seat, on the side next to the vehicle door, and clicks in place. The newborn protection insert is for babies from 4 to 10 lb and slides behind the infant support cushion; it must not be used without that cushion. The newborn harness pads replace the standard pads for small infants, and are swapped back once the child needs more padding. The 3QXT also keeps the anti-rebound bar.

Source: Diono Radian 3Q SafePlus Series manual (PDF)

Rear-facing installation

Children under 22 lb or under one year old must ride rear-facing. Diono recommends the detachable rear-facing base and the anti-rebound bar for rear-facing installs. The base feet tuck into a flat seat bight, or sit flat without being pushed into an elevated one. The blue level line should be level with the ground. LATCH runs through the rear-facing belt path up to 35 lb; from 35 to 50 lb, reinstall with a locked seat belt. The seat should move less than 1 in at the belt path, and the head must be 1.5 in below the top of the shell.

Source: Diono Radian 3Q SafePlus Series manual (PDF)

Forward-facing and booster

Forward-facing runs from 22 to 65 lb and 30 to 57 in, with the buckle in the middle slot from 22 to 30 lb and the forward-most slot above 30 lb. The SafeStop is used from 22 to 40 lb, and the adjustable bottom is lowered over 25 lb. LATCH is allowed to 40 lb. The top tether is recommended in the US and required in Canada. Booster mode covers 40 to 120 lb and 40 to 57 in with the harness removed, shoulders at or above the 4th slot, and only a lap/shoulder belt, never a lap belt alone.

Source: Diono Radian 3Q SafePlus Series manual (PDF)

Cleaning the fabrics

Before washing, remove the memory foam from the seat pad, the newborn protection insert pad and the harness pads, and take the wedges out of the infant support and newborn protection insert; the manual says not to wash the memory foam or the wedges. The seat cover, infant support, newborn protection insert, buckle pad and harness pads can be machine or hand washed in cold water on a gentle cycle with mild detergent, then dried flat in the shade. Bleach, ironing and dry cleaning are ruled out. The harness and buckle straps are spot cleaned with warm water and mild soap and never soaked.

Source: Diono Radian 3Q SafePlus Series manual (PDF)

Is the Radian 3QXT SafePlus 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 3QXT 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 3QXT SafePlus All-in-One Convertible Car Seat: common questions

How wide and heavy is the Radian 3QXT?

Diono lists it at 28.5 in tall, 17 in wide and 16 in deep, with a seat weight of 32 lb. Folded, the depth drops to 11.5 in.

Diono: Radian 3QXT SafePlus dimensions (opens in a new tab)

How much front-to-back room does the 3QXT need rear-facing?

Diono says a rear-facing 3QXT uses 30 to 36 in between the vehicle's back seat and the back of the front seat, depending on seat shape and contour.

Diono: Radian 3QXT SafePlus rear-facing room (opens in a new tab)

Can I use the Radian 3QXT on a plane?

The manual says it is certified for aircraft only in harness mode. Use the lap belt installation rear- or forward-facing, after shortening the aircraft buckle and asking the flight attendant for a seat belt extender. Booster mode is not certified.

Diono Radian 3Q SafePlus Series manual (PDF) (opens in a new tab)

When does the Radian 3QXT expire?

The manual says ten years from the date of purchase, with 8 years in the 5-point harness and 2 years in booster mode.

Diono Radian 3Q SafePlus Series manual (PDF) (opens in a new tab)

How is the Radian 3QX different from the 3QXT?

Diono lists the 3QX at 31.3 lb and 17 in wide. It has an adjustable headrest, infant insert and anti-rebound bar, without the 3QXT's newborn insert and Side Impact Management pod.

Diono Radian 3QX SafePlus support page (opens in a new tab)

How is the 3QXT FirstClass different from the 3QXT?

Diono lists the FirstClass at 32 lb and 17 in wide, with the same limits. In place of the anti-rebound bar it has an anti-rebound panel, and it adds a toddler liner.

Diono Radian 3QXT FirstClass SafePlus support page (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 3QXT SafePlus 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 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
Radian 3RXT All-in-One Convertible Car Seat	120 lb	—	—	10 years