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Harmony Youth Booster

The Harmony Youth Booster has a booster weight limit of 110 lb and has an expiration of 6 years, per Harmony. Harmony backless belt-positioning booster, model HMYBBLNYB-S6 per its US manual, used with the vehicle lap-and-shoulder belt.

  • 110 lbBooster to
See it on Harmony's site

When does it expire?

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Youth Booster: key facts

  • The Harmony Youth Booster works as a booster from 40 to 110 lb and 40 to 57 in tall, per Harmony.
  • Outgrown by height: "Child's ears MUST be below the top of the vehicle seat back/vehicle headrest."
  • It installs with vehicle 3-point lap-and-shoulder belt only.
  • Harmony says it expires 6 years after the date of manufacture.
  • Harmony says it isn't certified for aircraft.

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

How the Youth Booster stacks up

Against the 65 booster seats we track. The shaded band is where the middle half of them fall; the dot is this one.

Booster weight limit110 lb31st highest booster limit of 64

Within the typical range for booster seats (100 lb to 120 lb).

This one
100 lbmiddle 110 lb120 lb
Expiration6 years

Below the typical range for booster seats (8 years to 10 years).

This one
6 yearsmiddle 10 years12 years

What sets the Youth Booster apart

Measured against the 65 booster seats we compare, from each maker's published specs.

  • Booster weight limit: 110 lbin the middle half of the 64 booster seats that publish it (100 lb to 120 lb)

Next to its closest matches

  • Diono Cambria 2XTNext to it, the Youth Booster is 10 lb lower booster limit; 2 years shorter before it expires.
  • Diono SolanaNext to it, the Youth Booster is 10 lb lower booster limit; 2 years shorter before it expires.
  • Axkid UpNext to it, the Youth Booster is 10 lb lower booster limit; no load leg (the Up has it).

Flying with the Youth Booster

Harmony's label: “This restraint is NOT CERTIFIED for aircraft use.” American lists “Booster seats with no approval label or shoulder harness” under seats and devices not approved for use on board (source).

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

  • Maker states 40-100 lb and 40-57 in on the manual cover
  • Maker states the expiry date is on the underside of the base

Worth checking

  • Manual states it is not compatible with LATCH
  • Manual gives no seat weight, dimensions or age range

Where to buy the Youth Booster

Prices and availability change. We may earn a commission from some links.

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

Harmony Youth Booster
TypeBooster
Booster weight40–110 lb
Booster height40–57 in
Head ruleChild's ears MUST be below the top of the vehicle seat back/vehicle headrest.
Installationvehicle 3-point lap-and-shoulder belt only
Load legNo
Anti-rebound barNo
RotatesNo
Aircraft labelNot certified for aircraft
Expires after6 years

Compare the Youth Booster with

How each closest rival differs from the Youth Booster, from the makers' specs.

Ask the meadow

Youth Booster: questions answered

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

Can you bring the Harmony Youth Booster on a plane?

Harmony doesn't list it as certified for aircraft, so it can be checked as luggage but not used in the plane seat. See seats approved for planes.

Is it OK to buy a used Youth Booster?

NHTSA publishes guidance on used car seats on its car seat page. Harmony lists a lifespan of 6 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 booster seats

Where these specs come from

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