16.7 inches wide, according to its listing.
Car setup / three-across seats
Graco SlimFit3 LX vs. Diono Radian 3RXT: compare the listing specs
The Graco listing gives a 16.7-inch width; the Diono facts list four modes and rear-facing use up to 50 lb, with no numeric width. Those figures do not confirm a three-across fit, so check your vehicle manual and seat manual.
Both listings say rear-facing use up to 50 lb.
A listing width does not confirm your vehicle row.
Car-seat details
What does the listed width tell you?
Graco gives a numeric width and three weight ranges. The Diono listings describe both Radian seats as three-across models, but the supplied facts give no numeric width for either.
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Graco / 3-in-1 seat
Graco SlimFit3 LX
Consider it when: a numeric listed width is useful for your paper comparison.
Published specs: 16.7 inches wide; rear-facing harness 5-40 lb, forward-facing harness 22-65 lb, and highback booster 40-100 lb.
Limit: its listing describes it as fitting three across, but that does not confirm a fit in a specific vehicle row.
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Diono / 4-in-1 seat
Diono Radian 3RXT SafePlus
Consider it when: the listing’s four modes and rear-facing use up to 50 lb match the range you are comparing.
Published specs: the listing gives an overall 4-120 lb range, rear-facing use up to 50 lb, and a 12-position headrest.
Limit: the supplied listing facts say it fits three across but give no numeric width.
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Diono / companion option
Diono Radian 3QX
Consider it when: the listing’s fold-for-travel feature matters to your comparison.
Published specs: four modes, an overall 4-120 lb range, rear-facing use up to 50 lb, and a seat that folds for travel or compact storage.
Limit: the supplied listing facts describe it as three-across but do not give a numeric width.
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Which listing detail do you need?
Need a numeric widthStart with GracoIts listing gives 16.7 inches and three child weight ranges.See listed dimensions
Rear-facing rangeCompare the Diono listingsThe Radian 3RXT and 3QX listings say rear-facing use goes up to 50 lb.See the listed ranges
Travel storageCheck the 3QX listingIts listing says the seat folds for travel or compact storage.See the companion option
Listing comparison
What do the listing facts show?
| Listing detail | Graco SlimFit3 LX | Diono Radian 3RXT SafePlus | Diono Radian 3QX |
|---|---|---|---|
| Numeric seat width | 16.7 inches. | Not stated in the supplied listing facts. | Not stated in the supplied listing facts. |
| Modes and child weight range | 3-in-1: rear-facing harness 5-40 lb; forward-facing harness 22-65 lb; highback booster 40-100 lb. | 4-in-1; overall range 4-120 lb. The supplied facts do not split the range by mode. | 4-in-1; overall range 4-120 lb. The supplied facts do not split the range by mode. |
| Rear-facing limit | Harness range listed to 40 lb. | Up to 50 lb. | Up to 50 lb. |
| Other listed detail | 10-position no-rethread harness and headrest adjust together. | One-hand, 12-position headrest adjustment. | Folds for travel or compact storage. |
| Three-across wording | Listing says it fits three car seats across. | Listing says it fits three across. | Listing says it fits three across. |
Use the Graco width to narrow your options. For the exact row and installation, check your vehicle manual and seat manual.
No-buy
When can you skip buying another seat?
If your current seat and vehicle setup match both manuals, you may not need another seat just to compare widths. Check your vehicle manual and seat manual before changing the seat, position, or mode.
Before you decide
What should you check in your vehicle row?
- Use the Graco width as a starting point.The supplied Diono facts do not give a numeric width.
- Read both manuals.Check your vehicle manual and seat manual for the exact row, seat position, and installation instructions.
- Compare the seat you plan to use.The Radian 3QX listing describes a folding feature. The supplied Radian 3RXT facts do not mention one.
Read next
Car seat fit and vehicle guides
FAQ
Common questions about these car seats
Does the Graco SlimFit3 LX listing's 16.7-inch width confirm three seats will fit?
No. The listing describes the SlimFit3 LX as fitting three across and gives a 16.7-inch width. A published width does not confirm a fit in your row. Check your vehicle manual and seat manual.
What weight ranges does Graco list for the SlimFit3 LX?
The listing gives 5-40 lb rear-facing harness, 22-65 lb forward-facing harness, and 40-100 lb highback booster ranges.
Does the Diono Radian 3RXT listing give a numeric width?
No. The supplied listing facts describe it as a slim-fit three-across seat but do not give a numeric width. Check your vehicle manual and seat manual for your row.