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  • Britax One4Life Slim All-in-One Car Seat, 10 Years of Use, 17.5” SpaceSaver Design, Converts from Rear-Facing Infant Car Seat to Forward-Facing Booster Seat, ClickTight Installation, Sea Foam
  • Britax One4Life Slim All-in-One Car SeatBritax Child Safety

Britax One4Life Slim All-in-One Car Seat, 10 Years of Use, 17.5” SpaceSaver Design, Converts from Rear-Facing Infant Car Seat to Forward-Facing Booster Seat, ClickTight Installation, Sea Foam

4.5 out of 5 stars (22)
Currently unavailable.
We don't know when or if this item will be back in stock.
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Maximum Weight Recommendation 120 Pounds
Minimum Height Recommendation 18 Inches
Minimum Weight Recommendation 5 Pounds
Maximum Height Recommended 49 Inches
Rear Facing Maximum Weight 50 Pounds
Forward Facing Maximum Weight 120 Pounds
Forward Facing Minimum Weight 30 Pounds
Forward Facing Car Seat Minimum Height 35 Inches
Rear Facing Car Seat Maximum Height 49 Inches
Installation Type Seat Belt
Orientation Rear and Forward Facing
Harness Type 5-Point
Number of Height Positions 15

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Britax One4Life Slim All-in-One Car Seat, 10 Years of Use, 17.5” SpaceSaver Design, Converts from Rear-Facing Infant Car Seat to Forward-Facing Booster Seat, ClickTight Installation, Sea Foam

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Product Description

The One4Life(R) Slim all-in-one car seat takes your child from birth to big kid with trusted Britax safety, ClickTight(R) installation, and a slim SpaceSaver(TM) design. As a convertible and harness-2-booster seat in one, it grows with your child for 10 years. It starts rear-facing with an extended capacity of up to 50 lbs., so your child can ride rear-facing longer. It easily converts to forward-facing toddler mode (up to 65 lbs.) and high-back belt-positioning booster mode (up to 120 lbs.) when your child is ready. With a slim outside and spacious inside, the 17.5” seat is designed to fit 3 across* without compromising safety and comfort. ClickTight helps you install with confidence, every time. The base and shell are easy to wipe down for hassle-free cleanup. The car seat cover is safe to machine wash and dry, and it’s naturally flame-retardant with no added FR chemicals. One4Life Slim features a high-strength steel frame, a SafeCell(R) crumple zone, and a V-shaped tether. As your child grows, you can easily adjust the 15-position no-rethread harness and headrest with one hand. With cooling channels, premium padding, three infant inserts, and built-in armrests, your child will love every ride. *Britax cannot guarantee 3-across fitment in all vehicles.

From the manufacturer

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Customer reviews

4.5 out of 5 stars
22 global ratings
Box arrived completely open
4 out of 5 stars
Box arrived completely open
I like the car seat and baby won’t be here until February to try it out however, the box arrived completely open with all the tape cut on it. It wasn’t one piece of tape, it was every single piece on the box. Some of the plastic covering had been cut as well. The actual seat looks fine it just makes me uneasy that it was completely open upon delivery.
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Top reviews from the United States

  • TimmboBaggins
    5.0 out of 5 stars Britax One4life Slim All in one car seat.
    Reviewed in the United States on February 25, 2026
    Verified Purchase
    This seat is comfortable and has many features that make it a great seat. It is a little heavier than the car seats found at discount stores but this makes it a more solid product.
    Helpful
     Report
  • Wendy
    5.0 out of 5 stars Britax for the win!
    Reviewed in the United States on December 15, 2025
    Verified Purchase
    This car seat is the perfect size for our Tesla model y. It needs to be in a side seat for the anchors to properly work. It’s great for traveling because of how thick the padding is and how comfortable it keeps my kiddo. The buckles are easy enough for her to do herself and the cup holders are everyone’s favorite.
    Helpful
     Report
  • April
    5.0 out of 5 stars Easy install
    Reviewed in the United States on December 28, 2025
    Verified Purchase
    Easy install! Super quality nice car seat. Definitely recommend
    Helpful
     Report
  • Jessica Lee James
    5.0 out of 5 stars Britax is a favorite once again
    Reviewed in the United States on November 1, 2025
    Verified Purchase
    Color as expected, easy to install, slightly heavy but we bought two so we won’t need to switch from one car to another anyway
    2 people found this helpful
    Helpful
     Report
  • Elizabeth Dudley
    4.0 out of 5 stars Box arrived completely open
    Reviewed in the United States on December 22, 2025
    Verified Purchase
    I like the car seat and baby won’t be here until February to try it out however, the box arrived completely open with all the tape cut on it. It wasn’t one piece of tape, it was every single piece on the box. Some of the plastic covering had been cut as well. The actual seat looks fine it just makes me uneasy that it was completely open upon delivery.
    Customer image
    Elizabeth Dudley
    4.0 out of 5 stars
    Box arrived completely open

    Reviewed in the United States on December 22, 2025
    I like the car seat and baby won’t be here until February to try it out however, the box arrived completely open with all the tape cut on it. It wasn’t one piece of tape, it was every single piece on the box. Some of the plastic covering had been cut as well. The actual seat looks fine it just makes me uneasy that it was completely open upon delivery.
    Images in this review
    Customer image Customer image Customer image
    Helpful
     Report
  • B Mc
    3.0 out of 5 stars Comfortable
    Reviewed in the United States on December 14, 2025
    Verified Purchase
    The belt to tighten is hard to pull!
    Helpful
     Report
  • Jess
    1.0 out of 5 stars Used not new
    Reviewed in the United States on April 21, 2025
    Verified Purchase
    Would give zero stars if I could - we were sent a USED seat!
    3 people found this helpful
    Helpful
     Report
  • JWL
    1.0 out of 5 stars Customers beware of Sub-par Britax Customer Service
    Reviewed in the United States on April 18, 2025
    Beware customers of Britax. Worse customer service experience that I have experienced. Am wondering how a supposedly "professional" company is willing to operate with such bad customer service and contact information. I attempted to contact the Britax customer service via their telephone number advertised in their web site, i.e., BOB, who replied with a message "we are currently on vacation". Well, thank you for informing me of your vacation plans, BOB, but who know when you will be returning and if you will answer my calls and messages? As prompted by the Britax answering machine to "leave a message", but I was transferred to a non-existing and non-responsive number. If you are purchasing a Britax children car seat, then do not expect customer service assistance, let alone anything responsive" customer service. A real disappointment: I now regret my purchase of (expensive) Britax car seats.
    Helpful
     Report

Product Summary: Britax One4Life Slim All-in-One Car Seat, 10 Years of Use, 17.5” SpaceSaver Design, Converts from Rear-Facing Infant Car Seat to Forward-Facing Booster Seat, ClickTight Installation, Sea Foam

From Britax

4.5 out of 5 stars, 22 ratings

Customer reviews

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About this Item

  • All-in-One Car Seat: One4Life(R) Slim is a convertible and harness-2-booster seat in one! It easily converts from a rear-facing infant and toddler seat (5-50 lbs.) to a forward-facing seat (30-65 lbs.) to a high-back booster seat (40-120 lbs.)
  • ClickTight(R) Installation: Install with confidence in 3 easy steps: pinch to open, thread and buckle, click it closed!
  • SpaceSaver(TM) Design: Slim outside, spacious inside! The 17.5” seat is designed to fit 3 across without compromising on trusted Britax safety and premium comfort *Britax cannot guarantee 3-across installation fitment in all vehicles
  • Premium Car Seat Cover: Features a soft knit fabric with woven mélange accents that are made from recycled polyester; the cover is safe to machine-wash and dry and naturally flame retardant with no added FR chemicals
  • Trusted Britax Safety: Features a patented V-shaped tether, SafeCell(R) technology, a high-strength steel frame, and two layers of energy management
  • Comfortable Rides: This slim car seat includes soft comfort pads, built-in mesh cooling channels, three infant inserts, plush padding, and a tag-free headrest
  • Easy to Adjust: The 15-position no-rethread harness and headrest adjust together easily with one hand, and the 9-position recline has an easy-read indicator to help you find the correct angle for your vehicle
  • Slide-Out Cup Holders: The dishwasher-safe cup holders slide out with ease for convenient cleaning and click back into place for a secure attachment during rides
  • Accessible Color-Coded Belt Paths: Make it easy to route the seat belt through the correct path for each car seat mode
  • Hassle-Free Cleanup: Extra space between the shell and base means you can clean under the seat with ease – and with minimal grooves in the seating area and base, you can wipe it down with no fuss

Product Description

The One4Life(R) Slim all-in-one car seat takes your child from birth to big kid with trusted Britax safety, ClickTight(R) installation, and a slim SpaceSaver(TM) design. As a convertible and harness-2-booster seat in one, it grows with your child for 10 years. It starts rear-facing with an extended capacity of up to 50 lbs., so your child can ride rear-facing longer. It easily converts to forward-facing toddler mode (up to 65 lbs.) and high-back belt-positioning booster mode (up to 120 lbs.) when your child is ready. With a slim outside and spacious inside, the 17.5” seat is designed to fit 3 across* without compromising safety and comfort. ClickTight helps you install with confidence, every time. The base and shell are easy to wipe down for hassle-free cleanup. The car seat cover is safe to machine wash and dry, and it’s naturally flame-retardant with no added FR chemicals. One4Life Slim features a high-strength steel frame, a SafeCell(R) crumple zone, and a V-shaped tether. As your child grows, you can easily adjust the 15-position no-rethread harness and headrest with one hand. With cooling channels, premium padding, three infant inserts, and built-in armrests, your child will love every ride. *Britax cannot guarantee 3-across fitment in all vehicles.

Options Available

Color

  • Glacier Graphite
  • Graphite Onyx
  • Mineral Gray
  • Mineral Gray 2.0
  • Onyx Stone
  • Parchment
  • Parchment 2.0
  • Raven Black
  • Raven Black 2.0
  • Sea Foam 2.0
  • Teak

Style

  • One4Life
  • One4Life Slim
Browse all available options

Important Information

Safety Information

  1. To learn about the safe use of car seats and correct installation, visit the <a href="https://www.nhtsa.gov/equipment/car-seats-and-booster-seats?utm_source=amazon&utm_medium=amazon-details&utm_content=nhtsa-car-seats-main" target="_blank">National Highway Traffic Safety Administration (NHTSA)</a>. Disclaimer: NHTSA doesn't endorse this item. The link is for informational purposes.
  2. To learn about the safe use of car seats and correct installation, visit the <a href="https://www.nhtsa.gov/equipment/car-seats-and-booster-seats?utm_source=amazon&utm_medium=amazon-details&utm_content=nhtsa-car-seats-main" target="_blank">National Highway Traffic Safety Administration (NHTSA)</a>. Disclaimer: NHTSA doesn't endorse this item. The link is for informational purposes.

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