Britax Marathon ClickTight vs Diono Radian 3QXT

Both are convertible car seats — here are their published manufacturer specs side by side.

This compares published manufacturer specs — not safety or fit advice. The seat's manual, your vehicle's manual, NHTSA's tools and a certified CPST are the fit-and-safety authority; always check them before installing.

As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. Weight ranges are the manufacturer's published limits across all modes.

How they differ

• the Diono Radian 3QXT is listed narrow (roughly ≤17″) for fitting three across a back seat; the Britax Marathon ClickTight isn't listed narrow
• the Diono Radian 3QXT lists extended rear-facing (a higher rear-facing weight limit, ~40-50 lb); the Britax Marathon ClickTight doesn't

Published limits

Britax Marathon ClickTight: Rear-facing: 5–40 lb and 49″ or less. Forward-facing: 22–65 lb and 49″ or less (printed limits, same height cap both modes).

Diono Radian 3QXT: All-in-one (rear-facing → forward-facing harness → high-back booster; no backless mode found in manual). Sourced from Diono's "Radian 3Q SafePlus Series" manual, which covers 3QX SafePlus / 3QXT SafePlus / 3QXT FirstClass SafePlus together with shared weight/height requirements — this is Diono's current commercial name for what most retailers list simply as "Radian 3QXT" (confirmed via Diono's own store URL). No age gate printed for forward-facing (differs from the Radian 3RXT manual, which prints "at least 1 year old" — only the 22 lb weight floor applies here). Expired 10 years from date of purchase.

Printed verbatim in the manufacturer's manual (Britax Marathon ClickTight User Guide (Canada, P03810500B) · Diono Radian 3Q SafePlus Series Instruction Manual); “—” = not published for that mode, “not yet sourced” = we haven't read that manual yet, not that the seat has no limit. How we source these →

Recall record

Britax — 22 on NHTSA's record · Diono — 2 on NHTSA's record.

That is the record of the brand — not a verdict on these models. A recall names specific models and manufacture-date ranges, and a seat missing from the record is not "recall-free": check nhtsa.gov/recalls with the model and date of manufacture on your seat's label. Source: NHTSA, retrieved 2026-09-05.

Where to buy

Britax Marathon ClickTight

See price on Amazon

Diono Radian 3QXT

See price on Amazon

As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. Affiliate links never affect our specs or which seats we compare.

FAQ

What's the difference between the Britax Marathon ClickTight and the Diono Radian 3QXT?
The Britax Marathon ClickTight is FAA-approved for aircraft; the Diono Radian 3QXT is narrow for 3-across, extended rear-facing, FAA-approved for aircraft. Both are convertible car seats.

Which fits three across, the Britax Marathon ClickTight or the Diono Radian 3QXT?
The Diono Radian 3QXT is listed narrow (~≤17″) for 3-across; the Britax Marathon ClickTight isn't. Three-across fit still depends on your exact vehicle — confirm before buying.

Which is right for my car and child, the Britax Marathon ClickTight or the Diono Radian 3QXT?
That depends on your specific vehicle and child — this page compares published manufacturer specs only, not fit or safety. Check the seat manual, your vehicle manual, NHTSA's car-seat finder and ideally a certified CPST before deciding.

More convertible comparisons: Britax Marathon ClickTight vs Diono Radian 3RXT · Britax Boulevard ClickTight vs Clek Fllo · Britax Boulevard ClickTight vs Diono Radian 3QXT · Britax Boulevard ClickTight vs Diono Radian 3RXT · all convertible seats · all comparisons