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

Diono Radian 3RXT 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 26.5 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 3RXT SafePlus All-in-One Convertible Car Seat for?

The Radian 3RXT SafePlus is a folding all-in-one car seat. Diono's shared SafePlus manual lists rear-facing from 4 to 50 lb and 18 to 44 in, a forward-facing harness from 26.5 to 65 lb and 30 to 57 in, and booster mode from 40 to 120 lb. It expires ten years from the date of purchase.

Reasons to consider it

Rear-facing up to 50 lb or 44 in, per the manual
Harness modes certified for aircraft, using the lap belt routing
A detachable rear-facing base, plus a blue level line for installs without it
Folds in on itself and fastens shut with a red carry strap

Things to weigh up

LATCH is limited to 35 lb rear-facing and 40 lb forward-facing
Booster mode is not certified for use on aircraft
Diono lists the seat at 30.6 lb, so moving it between cars takes effort
The anti-rebound panel, SIM pod and comfort insert are listed only for select models

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

It suits a family that wants one seat for rear-facing, harnessed forward-facing and booster use, and accepts switching from LATCH to the vehicle belt as the child grows. Diono lists it at 17 in wide and 30.6 lb. The main trade-off is that LATCH stops at 35 lb rear-facing and 40 lb forward-facing. One manual covers this seat, the Radian 3R SafePlus and the 3RXT SafePlus Max with the same limits, and it does not say which optional parts each version includes.

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 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 harness26.5 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 SafePlus All-in-One Convertible Car Seat weight, height and age limits?

Diono Radian 3RXT 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	LATCH installation limited to 35 lb
Forward-facing harness	26.5 to 65 lb	30 to 57 in	Not published	26.5-30 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 SafePlus 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

LATCH covers 4 to 35 lb rear-facing. From 35 to 50 lb the manual says to reinstall with the vehicle seat belt, which is rated from 4 to 50 lb as a lap/shoulder or lap-only install. Diono recommends the detachable rear-facing base, with its feet tucked into the seat bight. If the bight is elevated, do not push the feet into it, because that changes the recline. If the base will not work, remove it and use the blue recline line on the label, which should be level with the ground. Test at the rear-facing belt path: it should move less than 1 in. The adjustable bottom is not used rear-facing.

Source: Diono Radian SafePlus Series manual (PDF)

Forward-facing: tether, SafeStop and the adjustable bottom

Diono requires the top tether forward-facing. LATCH is allowed from 26.5 to 40 lb, then the manual says to reinstall with the lap/shoulder belt for 40 to 65 lb. The SafeStop goes on the harness only for forward-facing children from 26.5 to 40 lb and must come off at 40 lb. The adjustable bottom must always be lowered forward-facing. Children from 26.5 to 30 lb use the middle buckle slot, and above 30 lb the forward-most slot. No more than 20% of the base should hang past the front of the vehicle seat cushion. With a lap belt and no tether anchor, use the lap belt cushion and the 5th harness slot.

Source: Diono Radian SafePlus Series manual (PDF)

Headrest, harness slots and outgrowing it

The headrest moves with a lever and clicks into place. With the harness in slots 1 or 2, the headrest sits level with the top of the seat. In slots 3 to 5, its bottom edge goes above the shoulders, level with the jaw. Rear-facing, the harness is at or just below the shoulders and the top of the head must be at least 1.5 in below the shell. Forward-facing, the harness is above the shoulders and the ears must be below the top of the shell. The child is too tall once the shoulders touch the bottom of the headrest at its highest setting, or above 57 in. Booster mode needs shoulders at or above the 4th slot.

Source: Diono Radian SafePlus Series manual (PDF)

Cover, washing and folding

The cover comes off in stages: the headrest cover first, then the snaps under the headrest flap, four plastic tabs under the seat bottom and the elastic around hooks near the lower booster guides. The included cover tool helps tuck the fabric back into the shell channel. Take out the memory foam before washing and do not wash it. Fabrics can be machine or hand washed cold on a gentle cycle and dried flat out of direct sun, with no bleach, iron or dry cleaning. The harness is spot cleaned only and must not be soaked. To fold, move the side wings in, pull the red levers and secure the carry strap.

Source: Diono Radian SafePlus Series manual (PDF)

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

What are the Radian 3RXT SafePlus weight and height limits?

Rear-facing is 4 to 50 lb and 18 to 44 in. The forward-facing harness is 26.5 to 65 lb and 30 to 57 in, and booster mode is 40 to 120 lb and 40 to 57 in. Infants under 26.5 lb or under one year old must ride rear-facing.

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

How wide and heavy is the Radian 3RXT SafePlus?

Diono lists it at 17 in wide, 16 in deep and 28.5 in tall, with a seat weight of 30.6 lb. Folded, the depth drops to 11.5 in while the width stays 17 in.

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

Can I use the Radian 3RXT SafePlus on a plane?

Only in harness mode. Use the aircraft lap belt with the rear-facing or forward-facing lap belt instructions, asking for a seat belt extender if needed. It is not certified for aircraft in booster mode, because aircraft seats have no shoulder belt.

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

How long does the Radian 3RXT SafePlus last?

The manual says not to use it once it is ten years from the date of purchase. It also says not to use it if any part is damaged or missing, or if the straps are cut or frayed.

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

How is it different from the 3RXT SafePlus Max?

Both are covered by the Radian SafePlus Series manual. For the Max it lists rear-facing at 4 to 50 lb, the forward-facing harness at 26.5 to 65 lb and booster mode at 40 to 120 lb, the same as this seat. The manual marks the anti-rebound panel, SIM pod and comfort insert as included only with select models, without naming them.

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

Can three Radian 3RXT SafePlus seats fit across?

Diono says a vehicle needs at least 51 in of seat width between the door handles to fit three Radian models. I would still check each seat's belt or LATCH access in the actual car.

Diono support: Radian 3RXT SafePlus 3-across space (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 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 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 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