The Britax One4Life® Slim All-in-One Car Seat grows with your child from birth to big kid—offering 10 years of trusted safety in a space-saving 17.5" design that can fit 3-across*. With ClickTight® installation, a high-strength steel frame, SafeCell® crumple zone, and naturally flame-retardant fabrics, it delivers Britax’s highest standards of protection. Transition seamlessly from rear-facing (up to 50 lbs.) to forward-facing (65 lbs.) to high-back booster mode (120 lbs.). Cooling channels, premium padding, and an easily adjustable 15-position harness ensure comfort at every stage.
3-in-1 longevity: Rear-facing, forward-facing, and high-back booster in one seat (5–120 lbs)
Slim SpaceSaver™ design: 17.5" width fits 3-across* while keeping interior space comfortable
Extended rear-facing up to 50 lbs for added safety
ClickTight® installation ensures confident, secure installs every time
High-strength steel frame + SafeCell® crumple zone + V-shaped tether
15-position no-rethread harness and headrest adjust together with one hand
Cooling channels and premium padding for all-day comfort
Machine-washable, machine-dryable cover with no added flame-retardant chemicals
Three removable infant inserts for a better newborn fit
Built-in armrests for comfort as they grow
Easy-clean base and shell
*Britax cannot guarantee 3-across fit in all vehicles.
Child Fit
Child Weight Range: 5–120 lbs
Rear-Facing Harnessed:
Weight: 5–50 lbs
Height: 18"–49"
Forward-Facing Harnessed:
Weight: 30–65 lbs
Height: 35"–49"
Belt-Positioning Booster:
Weight: 40–120 lbs
Height: 44"–63"
Seat Dimensions
Product Dimensions: 18.5" L × 17.5" W × 24.5" H
Seat Area (Depth / Width): 13.5" / 11.5"
Shoulder Width: 14"
Harness Slot Heights: 9"–19"
Buckle Strap Depths: 5.5"–8.75"
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Most orders are shipped via UPS Ground from our warehouse in Scottsdale, Arizona within 3 business day.
Transit times are typically 1 to 5 days. Please see our shipping page for estimated transit times to your location.
Strolleria accepts returns of new, unused items that are returned within 60 days of receipt. See our return policy for more information.
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