Expert Review: Real-World Insights on the Nuna LUMN Harness-to-Booster Seat

By Emily Brooks, CPST & Baby Gear Specialist

After over two decades of helping parents choose the right car seat—from hospitals to big-box retailers to boutique baby shops—I’ve learned that the best products don’t just check the boxes, they make everyday parenting easier. That’s why when Nuna introduced the LUMN, their first forward-facing-only harness-to-booster seat. I was eager to see how it performed in real life—not just on a showroom floor.

I tested the LUMN with a 7-year-old weighing approximately 50 pounds and measuring 44 inches tall. Our goal? A seat that’s safe, comfortable, and intuitive enough for parents to install and use confidently from day one. Here’s how the LUMN held up—and what makes it stand out.

A Closer Look at the Nuna LUMN

The Nuna LUMN marks the brand’s official entry into the harness-to-booster category. Unlike convertible seats like the RAVA or all-in-one options like the EXEC, the LUMN is forward-facing only, starting with a 5-point harness system for children 30–65 lbs (and at least 2 years old), then transitioning to a high-back booster seat for kids up to 110 lbs.

Design-wise, it shares styling cues with the EXEC—like its premium leatherette-wrapped leg rest, minimal seams, and sleek profile—but strips away the rear-facing bulk to focus on what families need in the final stages of car seat use. It’s packed with Nuna’s signature safety tech, including:

All-steel frame
Reinforced belt path
Aeroflex™ EPP foam for side-impact protection
Flame-resistant materials with no added FR chemicals

Unboxing & Setup: No Tools, No Fuss

Right out of the box, the LUMN impresses. It arrives fully assembled—no parts to attach, no confusing inserts. Installation materials (manual, labels) are neatly affixed to the seat and easy to review. Nuna even includes a tamper-evident safety seal on the box so you know it hasn’t been previously opened or used.

The seat comes in a high-end plastic protective wrap and is lightweight enough (26.2 lbs) to carry solo, despite its sturdy frame. It’s one of the few combination seats we’ve tested that feels truly premium, both in presentation and build quality.

Installation: One of the Best in Class

The LUMN uses Nuna’s True Tension™ door system, similar to what you’ll find on the RAVA and EXEC. Installation with a seatbelt is highly encouraged (and frankly easier than LATCH in this case). Here’s how it went:

Raised the headrest to its highest setting for easy access to the belt path.
Routed the seatbelt through the open belt path and pulled snug.
Closed the tensioning door—done.

No pushing, shoving, or re-routing. It locked down securely on the first try.

A tether strap completes the setup, and thanks to the open frame design, it works seamlessly even with vehicle headrests in place. The lack of a numbered recline guide is a minor nitpick, but otherwise, this seat offers one of the most stress-free installs we’ve encountered.

Fit & Adjustments: Built to Grow

Our test child had recently outgrown their RAVA harness by torso height, but still needed to be harnessed for a while longer. The LUMN’s higher harness slots—up to 18.5 inches—provided the perfect fit. That extra height is a game-changer for long-torsoed kids.

Once installed, we adjusted the seat:

Removed the body insert after confirming our tester was over 40 lbs.
Shifted the harness buckle to the closer position to prevent sliding.
Readjusted the no-rethread harness with a smooth glide.

Every adjustment can be made without uninstalling the seat—something many brands still miss. Even better, the crotch pad is buttoned on, meaning it stays in place instead of slipping off (a common gripe with other models).

Everyday Use: Kid-Approved Comfort

After just a few days of rides, our tester was clearly a fan. Highlights included:

Leg rest: A standout feature, allowing legs to stretch or bend comfortably.
Seat depth: Supportive enough for longer drives, helping avoid leg fatigue.
Fabric: Soft, breathable, and didn’t cause overheating—even during a midday nap.

And while this model came in a more neutral colorway, the luxe textures and curved silhouette still gave it that high-end feel that Nuna is known for.

Pros & Cons

✅ What We Loved

One of the easiest installations of any forward-facing seat
Premium materials throughout
High harness height for taller kids
No-rethread adjustments with thoughtful design touches
Integrated cupholders (not tacked on!)
Compact slim profile fits 3-across in many midsize vehicles

⚠️ Room for Improvement

No recline indicators (could be confusing for some)
Padding may need to be removed earlier than expected for ease of buckling
Only forward-facing—no rear-facing stage included
Cupholders are on the small side for larger water bottles

Comparison: LUMN vs RAVA vs EXEC

Feature	Nuna LUMN	Nuna RAVA	Nuna EXEC
Rear-Facing	❌	✅	✅
Highest Harness Height	18.5″	~16″	~17″
Leg Rest	✅ (Extendable)	❌	✅
Seat Weight	26.2 lbs	~27 lbs	~32 lbs
FAA-Approved	Harness Mode Only	✅	✅

If you already own the RAVA or EXEC and your child is ready for a forward-facing setup, the LUMN is a logical and attractive next step—especially for parents wanting to keep their child in a harness longer before switching to a booster.

Final Verdict

The Nuna LUMN is a thoughtfully engineered, beautifully designed car seat that hits the mark on safety, comfort, and ease of use. For parents entering the final stage of car seat life—forward-facing harness to booster—it’s hard to imagine a better option.

Expert Rating: 9.5/10

Whether you’re upgrading from a convertible seat or just want something slimmer, simpler, and stylish, the LUMN delivers.

About the Author

Emily Brooks, CPST, has over 20 years of experience in the child passenger safety space. As a nationally certified Child Passenger Safety Technician and baby gear specialist, she has personally installed thousands of car seats across every major brand and style. Emily has consulted for hospitals, first-time parents, and safety organizations, with a focus on making car seat safety accessible, stress-free, and practical for real families. Her hands-on expertise, attention to detail, and honest product testing make her a trusted voice for parents navigating their car seat journey.