Diono Radian 3QXT vs Britax Allegiance
Both are convertible car seats — here are their published manufacturer specs side by side.
| Spec | Diono Radian 3QXT | Britax Allegiance |
|---|---|---|
| Stage | Convertible | Convertible |
| Narrow (3-across) | ✓ | – |
| Extended rear-facing | ✓ | – |
| FAA-approved | ✓ | ✓ |
| Lightweight / travel | – | – |
How they differ
- the Diono Radian 3QXT is listed narrow (roughly ≤17″) for fitting three across a back seat; the Britax Allegiance isn't listed narrow
- the Diono Radian 3QXT lists extended rear-facing (a higher rear-facing weight limit, ~40-50 lb); the Britax Allegiance doesn't
Where to buy
Check the Diono Radian 3QXT price on Amazon →
Check the Britax Allegiance price on Amazon →
FAQ
What's the difference between the Diono Radian 3QXT and the Britax Allegiance?
The Diono Radian 3QXT is narrow for 3-across, extended rear-facing, FAA-approved for aircraft; the Britax Allegiance is FAA-approved for aircraft. Both are convertible car seats.
Which fits three across, the Diono Radian 3QXT or the Britax Allegiance?
The Diono Radian 3QXT is listed narrow (~≤17″) for 3-across; the Britax Allegiance isn't. Three-across fit still depends on your exact vehicle — confirm before buying.
Which is right for my car and child, the Diono Radian 3QXT or the Britax Allegiance?
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: Cosco Scenera NEXT vs Evenflo Revolve360 Slim · WAYB Pico vs Evenflo Revolve360 Slim · Evenflo Tribute LX vs Evenflo Revolve360 Slim · Graco Extend2Fit vs Cosco Scenera NEXT · all convertible seats · all comparisons