The new Chicco Fit3x is the latest ultra-slim car seat, and we’re blown away by everything Chicco managed to pack into this very narrow All-in-One! They squeezed an impressive number of features into a skinny car seat at a reasonable price. If you need to fit 3-across or just 2 seats side-by-side, the Chicco Fit3x should be on your shortlist!

Boasting tall harness slots, a narrowness that works in many 3-across situations, a robust ClickTight installation system, and naturally flame-retardant fabrics that are machine wash- and dryable, the Britax Poplar and Poplar S convertible carseats seem to be perfect. But nothing is that perfect, right?

The Britax One4Life Slim ClickTight All-in-One car seat has a mile-long list of features: a robust ClickTight belt-tensioning lockoff panel, a top harness slot height higher than most harness-to-booster seats, a top shoulder belt guide higher than most dedicated belt-positioning booster seats, flame retardant-free machine washable fabrics, and more! What else could we talk about in our review? Plenty.

Slim and ultra-narrow car seats are a hot trend right now. And while this new trend has been a godsend for many parents and caregivers looking to squeeze 3-across in their vehicle, it’s quite possible that the looming side-impact standard (FMVSS 213a), which will take effect on June 30, 2025, will force the discontinuation of some narrow harnessed car seats that aren’t able to comply with the stringent new requirements.