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Britax Grow with You Harness-to-Booster

The Britax Grow with You Harness-to-Booster forward-faces up to 65 lb, weighs 23 lb, and has an expiration of 9 years, per Britax. A forward-facing harness seat that converts to a belt-positioning booster up to 120 lb, without ClickTight.

  • $239.99List price
  • 65 lbHarness to
  • 120 lbBooster to
  • 23 lbSeat weight
See it on Britax's site

When does it expire?

Follow Britax

All harness-to-booster car seats

Grow with You Harness-to-Booster: key facts

  • The Britax Grow with You Harness-to-Booster forward-faces with a harness from 30 to 65 lb and 35 to 49 in tall; works as a booster from 40 to 120 lb and 44 to 63 in tall, per Britax.
  • Outgrown by height: "The top of the child's ears must be below the top of the head restraint when seated (harness and booster modes); harness straps must be in the closest position at or above the child's shoulders"
  • It installs with LATCH forward-facing + top tether (harness, child up to 45 lbs), seat belt forward-facing + top tether (harness) or booster: vehicle lap-shoulder belt (lower anchors may be used to position the seat).
  • Britax says it expires 9 years after the date of manufacture.
  • Britax lists it as certified for aircraft ("This restraint is certified for use in motor vehicles and aircraft when used in harness mode. This restraint is not certified for aircraft use when used in booster mode because belt-positioning boosters require lap-shoulder belts not available in aircraft.").

From Britax's manual and published specs. Always follow the limits on your seat's labels.

How the Grow with You Harness-to-Booster stacks up

Against the 22 harness-to-booster car seats we track. The shaded band is where the middle half of them fall; the dot is this one.

Expiration9 years

Within the typical range for harness-to-booster car seats (8 years to 10 years).

This one
6 yearsmiddle 10 years10 years
Forward-facing limit65 lbHighest forward-facing limit of 22 harness-to-booster car seats

The same as most harness-to-booster car seats (65 lb).

This one
40 lbmiddle 65 lb65 lb
Weight23 lb8th lightest of 15

Within the typical range for harness-to-booster car seats (16 lb to 25 lb).

This one
9.1 lbmiddle 23 lb26.2 lb
Price$239.9912th lowest price of 18

Within the typical range for harness-to-booster car seats ($79.99 to $239.99).

This one
$54.99middle $139.99$349.99

What sets the Grow with You Harness-to-Booster apart

Measured against the 22 harness-to-booster car seats we compare, from each maker's published specs.

  • Weight: 23 lbin the middle half of the 15 harness-to-booster car seats that publish it (16 lb to 25 lb)

Next to its closest matches

Flying with the Grow with You Harness-to-Booster

Britax's label: “This restraint is certified for use in motor vehicles and aircraft when used in harness mode. This restraint is not certified for aircraft use when used in booster mode because belt-positioning boosters require lap-shoulder belts not available in aircraft.”

What airlines say about car seats:

  • American: “Each ticketed customer is allowed 1 stroller and 1 car seat to be checked free of charge” “If an unoccupied, adjoining seat is not available, the gate agent will check the safety seat to your final destination.” Source
  • Alaska: “We will transport your child's car seat and stroller free of charge as checked baggage.” Source
  • JetBlue: “Checking a child safety seat will not count towards your checked baggage allowance and there is no fee assessed” Source
  • Spirit: “One (1) car seat will be accepted per child as checked baggage at no charge.” Source
  • Frontier: “strollers and car seats can be checked for free.” Source
  • Allegiant: “There is no charge for checking or gate checking one car seat per fare-paying passenger.” Source
  • Breeze: “Child seats may be carried on board the aircraft if a seat has been purchased for the Infant or Child” Source

Quoted from each airline's page as of 2026-11-02.

Listed features

  • Harness to 65 lb, booster to 120 lb
  • Lighter than the ClickTight version
  • Nine-year life

Worth checking

  • No rear-facing mode

Where to buy the Grow with You Harness-to-Booster

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good to know
  • Check for recalls: Search the agency's recall list with the model number and date code from the label: NHTSA recall search.
  • Car seat use and installation: see NHTSA's car seat page, which also lists free car seat inspection by certified technicians. Check the label and the maker's instructions, and ask your pediatrician about your child.

Full specs

Britax Grow with You Harness-to-Booster
TypeHarness-to-booster
List price$239.99
Forward-facing weight30–65 lb
Forward-facing height35–49 in
Booster weight40–120 lb
Booster height44–63 in
Seat weight23 lb
Head ruleThe top of the child's ears must be below the top of the head restraint when seated (harness and booster modes); harness straps must be in the closest position at or above the child's shoulders
InstallationLATCH forward-facing + top tether (harness, child up to 45 lbs), seat belt forward-facing + top tether (harness), booster: vehicle lap-shoulder belt (lower anchors may be used to position the seat)
Load legNo
Anti-rebound barNo
RotatesNo
Harness heights9
Recline positions2
Aircraft labelCertified for aircraft, per the maker
No added flame retardantsYes
Expires after9 years

Compare the Grow with You Harness-to-Booster with

How each closest rival differs from the Grow with You Harness-to-Booster, from the makers' specs.

Ask the meadow

Grow with You Harness-to-Booster: questions answered

From Britax's published specs, last checked 2026-11-06.

Can you bring the Britax Grow with You Harness-to-Booster on a plane?

Yes, Britax lists it as certified for aircraft; look for the red-lettered label that says so. The FAA asks that a car seat go in a window seat so it doesn't block the aisle, and the crew will look for that label. It weighs 23 lb to carry through the airport.

Grow with You Harness-to-Booster or Bay Latch SI 3-in-1 Harness Booster: what's different?

By the makers' specs, the Grow with You Harness-to-Booster has no added flame retardants (maker's claim). See every spec side by side.

Is it OK to buy a used Grow with You Harness-to-Booster?

NHTSA publishes guidance on used car seats on its car seat page. Britax lists a lifespan of 9 years from manufacture for this model. Check the label and the maker's instructions, and ask your pediatrician about your child.

Still wondering? Write to us at hello@cribpicks.com and we'll look it up.

More harness-to-booster car seats

Where these specs come from

Last checked 2026-11-06. Spot something wrong? Tell us. Read our editorial and safety policy and corrections.