Diono Monterey® 4DXT Booster

Yellow Sulphur

The original 2-in-1 booster seat with one of a kind, easy-adjust, separate height and width expansion. Transforms from a high-back booster to a backless booster as your big kid grows. With 15 SafePlus® and style upgrades from the Monterey® 2XT.

Granted by the Insurance Institute for Highway Safety (IIHS), the BEST BET award is bestowed to car seats and boosters that provide good belt fit for typical ages approximately from 4 to 8 years old in almost any car, minivan, or SUV. The IIHS is an independent, scientific, and educational organization dedicated to reducing injuries and property damage from motor vehicle crashes through the education of consumers, policymakers, and safety professionals.

 15 Improvements

  • Re-modeled headrest improves side impact performance
  • Optimized headrest shape improves head containment in the case of a collision
  • Thicker headrest EPP for better child comfort and sleep support
  • Deeper side wings improve side impact performance
  • Built in 3-layer protection system
    • Layer 1 - added EPP on inside for shock absorption
    • Layer 2 - molded rigid shell casing
    • Layer 3 – EPS material added to outer shell to absorb impact forces
  • Breathable exoshell side panels with enhanced airflow
  • Ergonomically contoured base
  • Improved child seating position
  • Luxury AIRTEK foam provides additional seat base cushioning
  • Refined seat back design, width reduced by for optimized vehicle fit but without a reduction in seat capacity
  • Better access to vehicle seat belt buckles for easy installation
  • Improved belt positioning across the child’s waist
  • Upgraded, automotive inspired fabrics
  • Improved cup holder integration
  • Fully covered backrest to protect vehicle interior


  • 8 Years One Booster - for your big kid from 40 - 120 lb. It's all you will ever need.
  • Easy-adjust - 11-position headrest that grows up with your child. Engineered for safety and comfort with 2 layers of SafePlus® Side Impact Protection.
  • One of a kind - easy-adjust expandable backrest allows up to 6.5 in to grow with your big kid. With 4 layers of SafePlus® Side Impact Protection and deep padded cushioning.
  • Two built-in retractable 2-in-1 cup holder and snack tray - keeps your big kid's drink close at hand and stows away their essentials.
  • Our contoured premium soft fabrics - with layered foam padding that provide comfort and support can be easily removed for machine washing.
  • SafePlus® belt guides - easy access to seatbelt buckle help your big kid with self buckling - don't forget to check though!
  • Easy, quick and secure installation - engineered with automotive steel LATCH connectors and 2 easy adjust LATCH straps allow you to quickly tighten and secure your booster to your vehicle.
  • Engineered with side impact protection - our rigid shell is reinforced with 2 layers of high-impact aluminum and EPS energy absorbing foam,to protect the head, shoulders, and torso.


  • Minimum User Weight: 40 lb
  • Maximum User Weight: 120 lb
  • Maximum User Height: 63 in
  • Product Height: 27.2 in
  • Product Width: 20.5 in
  • Product Depth: 16.1 in
  • Seat Weight: 18.3 lb
  • Number of Head Support Positions: 11


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