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Harmony Defender 360° MAX 3-in-1 Deluxe

The Harmony Defender 360° MAX 3-in-1 Deluxe forward-faces up to 65 lb, weighs 18 lb, and has an expiration of 10 years, per Harmony.

  • 65 lbHarness to
  • 120 lbBooster to
  • 18 lbSeat weight
See it on Harmony's site

When does it expire?

Follow Harmony

All harness-to-booster car seats

Defender 360° MAX 3-in-1 Deluxe: key facts

  • The Harmony Defender 360° MAX 3-in-1 Deluxe forward-faces with a harness from 26.5 to 65 lb and 27 to 57 in tall; works as a booster from 40 to 120 lb and 34 to 57 in tall, per Harmony.
  • Outgrown by height: "Harness mode: Child's ears MUST BE BELOW top of the headrest."
  • It installs with LATCH (harness mode, not over 50 lbs), vehicle lap-and-shoulder belt, vehicle lap-only belt (harness mode) or top tether (harness mode).
  • Harmony says it expires 10 years after the date of manufacture.
  • Harmony lists it as certified for aircraft ("This child restraint is certified for use in aircraft ONLY when used WITH the harness.").

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

How the Defender 360° MAX 3-in-1 Deluxe 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.

Expiration10 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
Weight18 lb7th 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

What sets the Defender 360° MAX 3-in-1 Deluxe apart

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

  • Weight: 18 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 Defender 360° MAX 3-in-1 Deluxe

Harmony's label: “This child restraint is certified for use in aircraft ONLY when used WITH the harness.”

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

  • Manual lists harness use 22 - 65 pounds and booster use 40 - 120 pounds
  • Manual lists aircraft certification with the harness
  • Manual lists a one-hand headrest button

Worth checking

  • Manual says forward-facing only; no rear-facing limits

Where to buy the Defender 360° MAX 3-in-1 Deluxe

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 Defender 360° MAX 3-in-1 Deluxe
TypeHarness-to-booster
Forward-facing weight26.5–65 lb
Forward-facing height27–57 in
Booster weight40–120 lb
Booster height34–57 in
Seat weight18 lb
Head ruleHarness mode: Child's ears MUST BE BELOW top of the headrest.
Newborn insertInfant insert cushion: 'Harmony recommends that you use the infant insert cushion until your child has reached a minimum of 35 pounds (15.8 kg).'
InstallationLATCH (harness mode, not over 50 lbs), vehicle lap-and-shoulder belt, vehicle lap-only belt (harness mode), top tether (harness mode)
Load legNo
Anti-rebound barNo
RotatesNo
Harness heights9
Aircraft labelCertified for aircraft, per the maker
Expires after10 years

Compare the Defender 360° MAX 3-in-1 Deluxe with

How each closest rival differs from the Defender 360° MAX 3-in-1 Deluxe, from the makers' specs.

Ask the meadow

Defender 360° MAX 3-in-1 Deluxe: questions answered

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

Can you bring the Harmony Defender 360° MAX 3-in-1 Deluxe on a plane?

Yes, Harmony 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 18 lb to carry through the airport.

Defender 360° MAX 3-in-1 Deluxe or LUMN: what's different?

By the makers' specs, the LUMN has no added flame retardants (maker's claim). See every spec side by side.

Is it OK to buy a used Defender 360° MAX 3-in-1 Deluxe?

NHTSA publishes guidance on used car seats on its car seat page. Harmony lists a lifespan of 10 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.