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Diono Monterey 6XT SafePlus High-Back Booster

The Diono Monterey 6XT SafePlus High-Back Booster has a booster weight limit of 120 lb and has an expiration of 8 years.

  • 120 lbBooster to

When does it expire?

All booster seats

Monterey 6XT SafePlus High-Back Booster: key facts

  • The Diono Monterey 6XT SafePlus High-Back Booster works as a booster from 40 to 120 lb and 38 to 63 in tall, per Diono.
  • It installs with vehicle lap/shoulder belt (booster) or LATCH/UAS connectors + lap/shoulder belt.
  • Diono says it expires 8 years after the date of manufacture.
  • Diono says it isn't certified for aircraft.

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

How the Monterey 6XT SafePlus High-Back 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 limit120 lbHighest booster limit of 64 booster seats

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

This one
100 lbmiddle 110 lb120 lb
Expiration8 years

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

This one
6 yearsmiddle 10 years12 years

What sets the Monterey 6XT SafePlus High-Back Booster apart

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

Next to its closest matches

  • Harmony Youth BoosterNext to it, the Monterey 6XT SafePlus High-Back Booster is 10 lb higher booster limit; 2 years longer before it expires.

Flying with the Monterey 6XT SafePlus High-Back Booster

Diono's label: “THIS RESTRAINT IS NOT CERTIFIED FOR USE IN AIRCRAFT.” 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.

Where to buy the Monterey 6XT SafePlus High-Back 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

Diono Monterey 6XT SafePlus High-Back Booster
TypeBooster
Booster weight40–120 lb
Booster height38–63 in
Installationvehicle lap/shoulder belt (booster), LATCH/UAS connectors + lap/shoulder belt
Load legNo
Anti-rebound barNo
RotatesNo
Aircraft labelNot certified for aircraft
Expires after8 years

Compare the Monterey 6XT SafePlus High-Back Booster with

How each closest rival differs from the Monterey 6XT SafePlus High-Back Booster, from the makers' specs.

Ask the meadow

Monterey 6XT SafePlus High-Back Booster: questions answered

From Diono's published specs and retailer listings, last checked 2026-11-06.

Can you bring the Diono Monterey 6XT SafePlus High-Back Booster on a plane?

Diono 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 Monterey 6XT SafePlus High-Back Booster?

NHTSA publishes guidance on used car seats on its car seat page. Diono lists a lifespan of 8 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.