Both are booster 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 Solana 2 is listed narrow (roughly ≤17″) for fitting three across a back seat; the Cosco Topside isn't listed narrow
Published limits
Mode
Diono Solana 2
Cosco Topside
Booster (backless)
40–120 lb · 38–63 in
40–100 lb · 43–57 in
Useful life
8 yrs from purchase
10 yrs from manufacture
Diono Solana 2: Backless booster only (no high-back mode). No age requirement printed. Expired over 8 years from date of purchase (printed number, per manual). Weight/height range happens to match Diono's Monterey 4DXT (same booster weight class), sourced independently from Solana 2's own dedicated manual.
Cosco Topside: Backless booster only (no high-back mode). No age requirement printed (weight/height/ear-position only). Do not use more than 10 years after the date of manufacture (printed number, per manual).
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.
Need it before the due date or a trip? Amazon Prime includes fast delivery on eligible items, and eligible new members may be offered a free trial. Delivery speed and return terms vary by item, so check the listing in case a seat may not fit your car. See if you can try Prime free →
Affiliate link — we may earn a commission on qualifying sign-ups, at no extra cost to you. Current terms are on Amazon's page.
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 Diono Solana 2 and the Cosco Topside? The Diono Solana 2 is narrow for 3-across, lightweight/travel; the Cosco Topside is lightweight/travel. Both are booster car seats.
Which fits three across, the Diono Solana 2 or the Cosco Topside? The Diono Solana 2 is listed narrow (~≤17″) for 3-across; the Cosco Topside isn't. Three-across fit still depends on your exact vehicle — confirm before buying.
Which is right for my car and child, the Diono Solana 2 or the Cosco Topside? 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.
Citing these specs? Go ahead — published manufacturer data, last verified 2026-06-11. Copy a ready-made reference: