Britax Willow Rear-Facing Only Infant Carseat with Aspen Base Review

Britax Willow Brook Travel System Review: Willow Rear-Facing Only Carseat with Aspen Base, Including Brook Stroller

Just like vehicle manufacturers revamp their vehicle lineup every 6-8 years, so do most carseat manufacturers, and this year Britax added a new rear-facing only carseat and travel system to their collection: the Willow Brook Travel System. It’s always fun to learn about new carseats and their features, but before we do, we need to get our leaves in a pile (*wince*, sorry, that was bad!).

This is the Earth year 🌎 at Britax, I think. Hear me out. It’s really hard to come up with unique carseat names (just ask someone over at another carseat company 😉😉). I’m going to try to make this naming scheme as easy as possible for you. The Willow Brook Travel System is featured in this review; however, everything mentioned can be applied to the Willow S with Alpine base and Willow Brook S+ Travel System.

Willow Brook: travel system, which includes Willow rear-facing only infant seat/Aspen base and stroller

Willow: infant seat carrier (only available for purchase in the Willow Brook Travel System)

Aspen: base

Willow Brook Graphite Glacier Willow Brook Navy Graphite Willow Brook Onyx Graphite

Available for Purchase Separately:

Willow S: infant seat carrier with Alpine base

Alpine: base with anti-rebound bar

Willow S Glacier Onyx Willow S Graphite Onyx Willow S Jade Onyx Willow S Ruby Onyx

Willow Brook S+: travel system, which includes Willow S rear-facing only infant seat/base and stroller

Willow Brook S+ travel systemWillow Brook S+ travel systemWillow Brook S+ travel systemWillow Brook S+ travel system

Willow Brook | Willow Brook S Comparison

Willow Aspen (Base) Specs & Features:
  • Rear-facing only: 4-30 lbs.; 32″ or less and head must be 1” below top of seat
  • 4 harness height positions
  • 2 hip strap positions
  • 3 crotch strap/buckle positions
  • Thick energy-absorbing EPP foam
  • SafeCell crumple zone technology on the carrier
  • Euro belt path allowed when installed without the base
  • ClickTight belt-tensioning lockoff with red/green indicator on base
  • Multi-recline position base
  • Flame-Retardant Free SafeWash cover is machine washable
  • QR code on inside of box that leads you to assembly and installation videos
  • FAA-approved for use in an airplane
  • Follows NHTSA guidelines for replacement after a crash
  • 6 year lifespan before expiration
  • Made in China
  • MSRP $449.99 as travel system

Extra Aspen bases are available for $149.99.

Extra Alpine bases are available for $159.99.

Willow Aspen Measurements:
  • Harness slot heights: 5 ½”, 7 ½”, 9 ½”, 11 ½”
  • Lowest harness slot height without body insert: 6 ½ ”
  • Crotch strap/buckle positions (without insert): 2”, 3 ½”, 5”
  • Internal shell height: 22”
  • Length of base footprint: 18” (up to 4.7” of overhang off vehicle seat allowed)
  • Width of base at widest point: 14”
  • Width of carrier at widest point: 17”(outside of handle)
  • Carrier weight: 9.2 lbs. with insert; 8.8 lbs. without insert

Recline angle indicator – There is a pendulum recline indicator on both sides of the base.

For installation without the base, there is a white indicator sticker with blue arrows on each side of the carrier.

Noodles/Rolled towels – Allowed. If the built-in recline foot isn’t sufficient, put the foot back into its storage position and use noodles or a rolled towel.

Overhang Britax allows up to 4.7” for the base to hang off the edge of the vehicle seat. The manual I received with my carseat says 3”, so I clarified with our Britax contact. 4.7” is it.

Installation with LATCH – ClickTight is designed to be installed with a seat belt. There are instances where you may want to install with LATCH, such as if you have a carseat-friendly tilt for access to a 3rd row. Let me launch into my LATCH spiel: LATCH isn’t safer—it’s a convenience feature. It’s only safer if it yields a tighter installation, but with ClickTight (CT), you won’t have a problem getting that with the seat belt.

The Aspen/Alpine base has deluxe push-on LATCH connectors that look like staplers. Make sure they’re upright when you push them on the lower anchors.

The LATCH strap is attached to the base with a strap that you must shift to the side so it doesn’t interfere with closing the CT.

Center LATCH installation with non-standard LATCH spacing: Not allowed

Installation with seatbelt – Again, ClickTight is designed to be installed with a seat belt. Don’t even bother taking the LATCH belt out of its storage area.

I think people who have had experience with previous versions of CT will have the most difficulty installing this base. It’s different. If you’ve never experienced CT before, you’ll catch on fast here and have problems with future Britax carseats 😆. I made a quick video and uploaded it to Instagram Reels (@carseatblog) and YouTube.

Installation Tips:

  • Use more seat belt than you think you should.
  • Don’t lock your seat belt! The CT is a lockoff.
  • Make sure the lap/shoulder belt is all the way underneath the CT panel.
  • To uninstall the base, unbuckle the base first, before trying to open the CT panel. This releases the tension in the belt and makes it easier to open the CT panel. Teach this to everyone who may remove the base!

Inflatable Seat Belts

Britax has determined that none of current carseats can be installed with inflatable seat belts found in some Ford Motor Company and Mercedes vehicles. You must use LATCH to install an Aspen or Alpine base in these vehicles.

Installation without base – The Willow carrier can be installed safely without the base using the typical American belt routing method OR the Euro method. Using the American method, the carrier is secured directly to the vehicle with the lap portion of the seatbelt (do NOT place the shoulder belt through the belt path). This is very handy if you’re traveling by taxi or airplane. No need to lug the base around with you! However, you have to know how to lock the seatbelt in the vehicle that you’re going to be riding in.

With the Euro method, the lap belt also goes through the belt path across the top of the carrier, but the shoulder belt routes behind the back of the seat instead of resting against the back of the vehicle seat. This usually ensures a very stable installation where the seat stays more upright in a frontal crash.

Handle Any locked handle position may be used in the vehicle. Britax recommends the handle be in the upright, locked position when in the vehicle—they say the built-in ReboundReduce™ helps reduce rebound motion (learn about that here) in a crash. It surely reduces rebound in the upright position, but it would provide more anti-rebound effect if it had a more forward position over the feet.


Head and Body Support Inserts

The optional head pillow can be removed at any time.

The optional body support has a weight limit and must be removed when your child reaches 11 lbs.

Harness pads are optional. Everything is optional! Yay!

🚨 Adjustments to Make at 11 Pounds 🚨

The Willow/Willow S comes out of the box set for a newborn weighing less than 11 lbs. (Ha! Most are!) You must make these changes at 11 pounds:

  • Remove body support (this is the piece the baby sits on)
  • Change the length of the harness at the shoulders (move from inside loops to end loops on bottom of seat; see pg. 45 in the manual)
  • Change the hip harness slots to the outer position if you adjusted them to accommodate a tiny baby (see pg. 50 in the manual)

The Willow has the RightSize™ harness system, which is a fancy way of saying that it not only adjusts in height, but also adjusts in width at the hips. This is good if your baby has very small hips so you can tighten the lateral space at their hips and they won’t slide side-to-side. Two things with this:

  1. The smallest hip adjustment is only for babes 4-11 lbs., and
  2. There’s only 1 slot in the cover, which is both good and bad. It’s good in that it’s a frequent error we see that caregivers often don’t line the slots up with the slots in the cover. It’s bad in that there’s no obvious visual cue which hip slot you’re using unless you turn the seat over.

➡️ As techs, we’ll have to be flipping the seat over to check on this as a routine part checking this seat during an appointment.

➡️ I think you’ll need to make the adjustment to the smaller slots only for the smallest babies. I had it set on the smaller slots for baby H, but think she could have gone with either setting.

For height, use the closest harness slot that’s below the child’s shoulder.

The harness is smooth too!

My sweet little model, H, is 3 weeks old and about 7 lbs. She is the same size as the preemie doll we use to test our carseats and fit in the Willow very well. We had to work fast getting her in the seat and getting pics since she didn’t like being still or having her arms exposed to show the harness. It took two of us techs (one is a postpartum and infant care doula) trying to calm her and you can see how well that went 😆. She much preferred the stroller part of the review (see her happy in the stroller)! Alas, no reflection on the Willow since that’s how she responds to being strapped into her carseat and another one I had on-hand.

*A note about the Willow/Willow S not having a no-rethread harness (harness height adjusts by sliding up or down): I’m all in favor of that. Don’t get me wrong: no-rethread harnesses are great: they’re easy to adjust the harness height rather than having to manually take each harness strap off the splitter plate on the back of the carseat. But on an infant seat it’s no big deal. You don’t do it that often and it’s easy to do. Plus it adds bulk behind a child’s head that may push it forward and cause chin-to-chest issues (breathing), and it adds weight to a seat. So, yeah, if it can be done right (and it has been), it’s great. Phew! I’m done. ☺️

Cover/Ease of Use/Maintenance:

Removing the cover for cleaning is easy, but you must remove the canopy first as well as undo the harness from the metal splitter plate on the back of the seat. There are also a few elastic bands to unhook. It took me only a couple of minutes to do this. Reverse the steps to put it back on.

💡 To put the canopy back on, put the elastic around the circular hub first, then slide the plastic piece into the channel until it clicks in.

💡 Always take pics or a video as you take the cover off so you know which harness and buckle slots to use and where to tuck elastics. Britax also has a good video on changing the cover.

The harness is replaceable if it becomes nasty beyond cleaning.

Britax has one of the best manufacturer support pages with a robust FAQ, booklet manual, and video manual library. You can find a full complement of videos supporting the Willow Brook family of products.

They also have accommodated for compatibility with other manufacturers, both for using the Willow/Willow S with other strollers and using other carseats with Britax strollers. Manufacturers such as CYBEX, Nuna, Maxi-Cosi, and UPPAbaby are listed. You can find compatibility charts on their support page.

To clean the harness, wipe with a wet washcloth and a touch of mild soap and towel dry. DO NOT wash in the washing machine or use chemicals on it.

FAA-Approval/Lifespan/Crash Guidelines:
  • FAA certified for use on airplanes
  • 6 year lifespan before expiration

The Willow/Willow S must be replaced after a moderate to severe crash, using the NHTSA guidelines:

  • The vehicle is able to be driven away from the crash site.
  • The vehicle door nearest the car seat is not damaged.
  • None of the passengers in the vehicle were injured in the crash.
  • If the vehicle has air bags, the air bags did not deploy during the crash; and
  • There is no visible damage to the car seat.
The Brook Stroller

The Willow infant carseat with Aspen base currently is only sold with the Brook stroller as a travel system. The Alpine S is a standalone carseat or comes with the Willow Brook S+.

What does the Brook S+ have that the Brook doesn’t?

  • Parent tray (it’s a snack tray, let’s be real 😆) that has phone and 2 cup holders
  • Two-toned color scheme on the toddler chair

You come to CSB for carseat reviews and info and that’s our trained background—it’s been a long time since I used or needed a stroller, so my comments will be superficial at best (just so you know where I’m coming from on this one!).

After easy assembly following the video, the stroller was up and running, but not literally though since it’s not a jogger. The push is so smooth and easy—I loved it—and it turned on a dime. It is nothing like the ones I used for my kids that constantly ran over people’s feet despite my best intentions. It drove well over asphalt, concrete, and fake grass.

It has the requisite brakes on the back wheels. Folding was easy, though maybe too easy? I might have preferred the mechanisms down further on the handle so I wouldn’t be inclined to grab them without thinking.

First car is my Tesla Model X, second car is my daughter’s Nissan Kicks for trunk space comparison.

It’s light for a full-size stroller and I like that you can put the carseat on either facing you or facing out—same with the stroller seat. The stroller seat doesn’t recline to a full flat recline, so the infant seat must be used on the stroller frame until a baby has head and neck control.

Willow/Willow S Advantages:
  • 4 harness height positions with 2 hip slot positions
  • 3 crotch strap/buckle positions
  • Thick EPP foam
  • SafeCell crumple zone technology on the carrier
  • Euro belt path allowed when installed without the base
  • ClickTight belt-tensioning lockoff with red/green indicator on base
  • Multi-recline position base
  • FR-free cover is machine washable
  • Follows NHTSA guidelines for replacement after a crash
  • Large, quiet canopy that doesn’t interfere with handle
  • Fits preemies well
  • Smooth harness
  • Well-padded with optional-use inserts

(In fairness, these aren’t necessarily problems but I list them here to inform potential consumers of specific Willow/Willow S issues)

  • Lots of confusing names for things: the base is called something different from the carrier, the handle has a name in its upright position (ReboundReduce™), RightSize™ for the harness, etc.
  • ClickTight panel can be tricky to use if you don’t have it pulled up all the way
  • Have to remove canopy to take cover off for washing

Aside from the confusing naming scheme, the Britax Willow with Aspen Base that is included with the Willow Brook travel system is welcome update to the Britax rear-facing only infant seat lineup. Adding ClickTight to the Aspen and Alpine bases make for a meld-with-the-vehicle-seat installation. The ability to adjust the harness to get a more custom fit on a smaller baby will put new parents at ease when using the carseat at a time for the first time (or the second or third!).

Basic Infant Seat Safety

Infant seats are so commonplace that parents often copy what other parents are doing with their seats. I know my husband and I did, and that can be dangerous, especially when misuse rates top 90%. I’ve already covered some of the basics above regarding fit to your vehicle and child. So what do you see out and about that you shouldn’t copy yourself?

  • DO NOT put the carrier on top of a shopping cart
  • WHENEVER the child is in the carrier, ALWAYS buckle the entire harness and tighten it
    • Some parents unbuckle the crotch buckles when in a store or will only buckle the chest clip when buckling in baby, but that piece of plastic is not designed to withstand crash forces. Babies can also wiggle down in the seat and strangle on the chest clip.
  • Don’t leave the child in the carrier to sleep
    • Studies have shown that babies desat, or have a reduction in oxygen, when they sleep for too long in infant seats.
    • Remember that the rear-facing only infant carseat is a safety device, not a safe sleeping space

For more information on the Britax Willow Brook Travel System, visit Britax’s website:


Thank you to Britax for providing the Willow Brook Travel System sample for this review. No other compensation was provided. All opinions expressed are those of CarseatBlog.



  1. Kayla Falls February 15, 2024
  2. Jenny July 6, 2023

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