# Convertible car seats that fit three across Which convertible car seats fit three across in a single back seat? Clek Foonf: Confirmed a three\-across fit in a midsize sedan next to another seat and a booster, crediting the roughly 17 in width\. Diono Radian 3QX Ultimate: It fit two Radian 3QX seats plus an infant carrier in a mid\-size SUV and, per another parent, in a 2016 Toyota Tacoma\. Britax One4Life Slim: The review rates it 4\.8 out of 5 and calls it a strong choice, especially for fitting three seats across\. Britax One4Life Slim ClickTight All\-in\-One Car Seat: The seat is 17\.5 inches wide, described as slim enough to fit three across in most vehicles\. Diono Radian 3RX: The store says three seats will most likely fit when the rear row measures at least 51 inches \(129\.6 cm\) between armrests; vehicle\-belt installation may be necessary\. Diono Radian 3R SafePlus: The retailer says the slim\-fit design permits three seats across in most midsize vehicles\. Diono Radian 3QXT\+: At 17 inches wide the seat is stated to fit three across in most midsize vehicles\. DIONO Radian 3QX: Testing praised the narrow 17\-inch body for three\-across arrangements, but judged the seat heavy and bulky despite its ability to fold for travel\. Britax One4Life Slim All\-in\-One Car Seat: Shows the One4Life Slim next to a Britax Poplar and a Willow S infant seat, demonstrating three\-across fit\. ### 1. [Clek Foonf](/products/ucp/albeebaby-com/9501995139303) (sold by albeebaby\.com) Confirmed a three\-across fit in a midsize sedan next to another seat and a booster, crediting the roughly 17 in width\. - Three\-across fit: Confirmed a three\-across fit in a midsize sedan next to another seat and a booster, crediting the roughly 17 in width\. (review) - Width: Confirmed a three\-across fit in a midsize sedan next to another seat and a booster, crediting the roughly 17 in width\. (review) - Modes: Foonf is a convertible car seat designed for rear\-facing and forward\-facing use\. (listing) - Installation: At first the manual was needed often, but after a few weeks the seat could be installed in under a minute in both modes\. (review) ### 2. [Diono Radian 3QX Ultimate](/products/ucp/megababiesusa-com/5504254312601) (sold by megababiesusa\.com) It fit two Radian 3QX seats plus an infant carrier in a mid\-size SUV and, per another parent, in a 2016 Toyota Tacoma\. Recall notice: Health Canada and Transport Canada, 2024\-11\-25: [Transport Canada Recall \- 2024718 \- DIONO](https://recalls-rappels.canada.ca/en/alert-recall/transport-canada-recall-2024718-diono) (recall). The notice may cover only some serial numbers or dates of manufacture, which this listing does not show\. [What a match means](/recall-radar). - Three\-across fit: It fit two Radian 3QX seats plus an infant carrier in a mid\-size SUV and, per another parent, in a 2016 Toyota Tacoma\. (blog) - Width: The seat's 17\-inch width lets three Radian seats fit across a back seat with at least 51 inches between interior door handles\. (blog) - Modes: The store describes the Radian 3QX as a luxury standard convertible car seat\. (listing) - Installation: Testers got a secure install in about 10 minutes and found the manual and side stickers helpful\. (review) ### 3. [Britax One4Life Slim](/products/ucp/megababiesusa-com/8648873214206) (sold by megababiesusa\.com) The review rates it 4\.8 out of 5 and calls it a strong choice, especially for fitting three seats across\. - Three\-across fit: The review rates it 4\.8 out of 5 and calls it a strong choice, especially for fitting three seats across\. (review) - Width: The seat is 17\.5 in wide and Britax says it is designed to fit three across\. (guide) - Modes: One4Life Slim is a convertible and harness\-2\-booster seat in one\. (listing) - Installation: Owners repeatedly describe ClickTight installation as easy and secure, including one who used the seat from newborn\. (review) ### 4. [Britax \(listed by the store as Britax\-dc\) One4Life Slim ClickTight All\-in\-One Car Seat, SKU E1D407A\-OB](/products/ucp/albeebaby-com/9564436201703) (sold by albeebaby\.com) The seat is 17\.5 inches wide, described as slim enough to fit three across in most vehicles\. - Three\-across fit: The seat is 17\.5 inches wide, described as slim enough to fit three across in most vehicles\. (listing) - Width: The seat is 17\.5 inches wide, described as slim enough to fit three across in most vehicles\. (listing) - Modes: The seat is an all\-in\-one that converts to a booster and is stated to fit a child from 5 to 120 lb and up to 63 inches tall\. (listing) - Installation: ClickTight installation is done in three steps: pinch to open, thread and buckle, click it closed\. (guide) ### 5. [DIONO Radian 3RX](/products/ucp/anbbaby-com/4510182211670) (sold by anbbaby\.com) The store says three seats will most likely fit when the rear row measures at least 51 inches \(129\.6 cm\) between armrests; vehicle\-belt installation may be necessary\. - Three\-across fit: The store says three seats will most likely fit when the rear row measures at least 51 inches \(129\.6 cm\) between armrests; vehicle\-belt installation may be necessary\. (guide) - Width: - - Modes: This is an all\-in\-one convertible car seat with a steel core, designed for narrow three\-across arrangements\. (guide) - Installation: - ### 6. [Diono Radian 3R SafePlus](/products/ucp/anbbaby-com/8558162084126) (sold by anbbaby\.com) The retailer says the slim\-fit design permits three seats across in most midsize vehicles\. - Three\-across fit: The retailer says the slim\-fit design permits three seats across in most midsize vehicles\. (guide) - Width: It measures 28\.5 in high by 17 in wide by 16 in deep unfolded, and 11\.5 in deep folded\. (guide) - Modes: The manual covers all\-in\-one use from 4 to 120 lb\. (manual) - Installation: - ### 7. [Diono Radian 3QXT\+ \(Radian 3QXT FirstClass SafePlus\), model 53000\-NA\-01 \(Black Jet\) / 53001\-NA\-01 \(Gray Slate\)](/products/ucp/megababiesusa-com/7476789215486) (sold by megababiesusa\.com) At 17 inches wide the seat is stated to fit three across in most midsize vehicles\. - Three\-across fit: At 17 inches wide the seat is stated to fit three across in most midsize vehicles\. (guide) - Width: The seat measures 16 inches deep by 17 inches wide by 28 inches tall\. (listing) - Modes: Rear\-facing it is rated for children from 4 to 50 lbs\. (listing) - Installation: - ### 8. [DIONO Radian 3QX](/products/ucp/anbbaby-com/4748741541974) (sold by anbbaby\.com) Testing praised the narrow 17\-inch body for three\-across arrangements, but judged the seat heavy and bulky despite its ability to fold for travel\. Recall notice: Health Canada and Transport Canada, 2024\-11\-25: [Transport Canada Recall \- 2024718 \- DIONO](https://recalls-rappels.canada.ca/en/alert-recall/transport-canada-recall-2024718-diono) (recall). The notice may cover only some serial numbers or dates of manufacture, which this listing does not show\. [What a match means](/recall-radar). - Three\-across fit: Testing praised the narrow 17\-inch body for three\-across arrangements, but judged the seat heavy and bulky despite its ability to fold for travel\. (review) - Width: - - Modes: It is an all\-in\-one seat intended for use from birth through booster mode, with a stated overall capacity of 4–120 lb \(1\.8–54 kg\)\. (guide) - Installation: After a few practice attempts, the owner found installation straightforward, but recommended adjusting harness and buckle positions before placing the seat in the vehicle\. (review) ### 9. [Britax One4Life Slim All\-in\-One Car Seat](/products/ucp/strolleria-com/8129392967754) (sold by strolleria\.com) Shows the One4Life Slim next to a Britax Poplar and a Willow S infant seat, demonstrating three\-across fit\. - Three\-across fit: Shows the One4Life Slim next to a Britax Poplar and a Willow S infant seat, demonstrating three\-across fit\. (review) - Width: Measured 18 inches at its widest point, about 1\.5 inches narrower than the standard One4Life's 19\.5 inches\. (review) - Modes: One4Life Slim is an all\-in\-one convertible and harness\-2\-booster car seat\. (listing) - Installation: - Every value in the table is a fact RoboTrunk checked, linked to the page it came from\. A dash means no checked fact fills that cell\. Prices and stock change, so this page prints neither: each product name links to its RoboTrunk page, which shows them live\. Written 2026-10-28T02:56:01.471Z. ## Recall notices About the recall notices above: each matches a model named in a regulator's notice, as the index stood on 2026\-09\-25\. This listing is the brand and model a regulator's notice names\. Two AI models judged it so independently\. It does not mean the unit on sale is from an affected batch, that the store knew, or that the product is illegal where the store sells it; a US recall does not bind an Australian store\. The notice may cover only some serial numbers or dates of manufacture, which a listing does not show\. RoboTrunk never limits or blocks a purchase over a notice; read the notice and decide\. This page is published by RoboTrunk, a store built for shopping agents. The store named on this page sells the product and ships it. RoboTrunk is not the seller and never holds the money. Buying works in one path. 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