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Ships within 48 hours · Estimated delivery Jul 13 - Jul 18
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Description
britax safety first car seat Britax One4Life Slim All-in-One Car SeatThe One4Life Slim all in one car seat takes your child from birth to big kid with trusted Britax safety, ClickTight installation, and a slim SpaceSaver 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
The One4Life® Slim all-in-one car seat takes your child from birth to big kid with trusted Britax safety, ClickTight® installation, and a slim SpaceSaver™ 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® 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.
- All-in-One Car Seat: One4Life® 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.)
- 10 Years of Use: This slim all-in-one car seat grows with your child from 5 to 120 lbs. and up to 63” tall
- ClickTight® Installation: Install with confidence in 3 easy steps: pinch to open, thread and buckle, click it closed!
- SpaceSaver™ Design: Slim outside, spacious inside! The 17.5” seat is designed to fit 3 across without compromising on trusted Britax safety and premium comfort.
- Premium Fabrics: The woven mélange accents give the car seat cover a tailored look, while the soft knit fabric on the padding and inserts helps keep your child comfortable during every ride
- Woven Accents on the Exterior and Comfort Pads: Made from recycled polyester
- 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
- SafeWash® Fabrics: No more hand-washing or waiting for the cover to air-dry; just quick and easy cleanup so you can keep moving
- Naturally Flame-Retardant Cover: With no added FR chemicals
- Three Removable Infant Inserts: Help provide a better fit for infants 20 lbs. and under
- Accessible Color-Coded Belt Paths: Make it easy to route the seat belt through the correct path for each car seat mode
- 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
\Cup-Holder-Free Option: Remove the cup holders completely and insert the armrest caps to save additional space - 15-Position No-Rethread Harness and Headrest: Adjust together quickly and easily with one hand to help create the proper fit as your child grows; no rethreading, ever!
- Patented V-Shaped Tether with Staged-Release Stitches: Helps slow and reduce forward movement during a crash
- High-Strength Steel Frame: Reinforces the seat structure to help keep it sturdy and stabilized
- Quick-Push, 9-Position Recline with Easy-Read Indicators: Helps you find the most comfortable fit for your child and the correct angle for your vehicle
- SafeCell® Technology: Acts as a crumple zone, absorbing crash energy to help keep it away from your child
- Two Layers of Energy Management: The protective seat shell and foam-lined headrest help absorb impact energy and are designed to help keep your child's head, neck, and body safe
- Soft Comfort Pads: Help prevent the harness from rubbing against your child’s skin
- Flip-Forward Buckle Pad: Stays out of the way for easy boarding; made with extra padding for premium comfort
- Built-In Cooling Channels: Improve airflow to help keep your child comfortable
- Plush Padding: For superior comfort and a quiet ride
- Easy-Pull Harness Adjuster: Lets you tighten the harness using just one hand
- Harness Holder Slots: Keep the harness straps out of the way while your child gets in and out of the seat
- 5-Point Safety Harness with Diamond Weave Webbing: Provides adjustment points at the hips, shoulders, and between the legs
- Tag-Free Headrest: Supports your child’s head and neck without irritation
*Britax cannot guarantee 3-across fitment in all vehicles.
Specifications
- Dimensions: 24.5"H x 18.5"D x 17.5"W
- Weight: 28 lbs.
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.6 ★★★★★
Based on 2213 reviews
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Product Reviews
★★★★★ 5
Fit and Length
Size: X-Large, Color: (401) Royal / / White
Yeah this fits perfectly. Very soft, the color pops, keeps you warm. I use these under my sweatshirts, cable sweaters, and my flannel shirts. For me it's about the arm length and how well the item contours to the body to help with warmth. Thank you for getting this right.
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Reviewed in the United States on February 23, 2026
★★★★★ 5
Worth it.
Size: Small, Color: Black (001)/White
Living in North Dakota, staying warm is invaluable. UnderArmour Cold Gear is the only base layer the provides warmth, KEEPS warmth, and protects from the unforgiving wind. Every winter I go on the hunt for thermals, layering options and I always find others to be saggy or incredibly tight, either way, once I begin shoveling or snowblowering, and sweating, other products become soaked, sticking to skin, unbreathable and quickly your sweat stuck to your body under layers in now creating a cold,chill, freeze to your body, and on a -10F day, it can become a dangerous situation.
I honestly was hesitant to purchase UnderArmour, I felt it was too hyped up or paying for a name. BUT IT IS NOT. UnderArmour isn't a name, it is a company that has made the highest quality base layer, warmth, breathable and it really wicks sweat away; I may not know how it does it, but it works!
For sizing, I ordered a small in the women's longsleeve/turtleneck black coldgear. I'm 5ft and roughly 110lbs. I like the fit, it is meant to fit your body. I probably could wear an extra small, but I like the sleeve length in the small and it fits very well.
Stay warm folks!
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Reviewed in the United States on December 6, 2023
★★★★★ 5
Great cold gear
Size: Large, Color: White (100)/Black
Warm, very comfortable. I wear these all winter. The neck can be a little tight and the cut is definitely fitting. Its got thin like fleece on the inside that keeps you warm.
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Reviewed in the United States on November 3, 2025
★★★★★ 4
Tight but stays in place, comfy and keeps you warm
Size: Medium, Color: Charcoal Light Heather (019)/Black
I liked this shirt because it keeps me warm when I'm outside even at negative temperatures, I can work out comfortably in it and the sweat dries out soon; also, the interior of the shirt is made of a very comfortable material.
I don't like that this is very tight, cool if you want to use it under your usual sports clothes but if you want to use it as is I would suggest going up a size.
I use this shirt almost every day to work out during winter time, I've washed them several times and they still feel as comfortable as the first day.
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Reviewed in the United States on January 5, 2022
★★★★★ 5
Perfect for running!
Size: Small, Color: Black (001)/White
None of my running clothes make me feel as sexy as this underarmor does. It is so soft on the inside, which is an upgrade from their old version because I found one at the thrift store that is really scratchy. It has been through a cold wash and the dryer multiple times at this point and it is still holding up. The size is true. The material thickness is perfect for me between 45-35° F. And again with layers between 15-10° F. But I look forward more to my runs that I get to wear my underarmor. Nothing makes me feel more confident on the trail. And I love love love the turtleneck. I got all black because that is my favorite color to wear when I run and it looks perfect. It is a true black.
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Reviewed in the United States on March 3, 2026