Britax Marathon 70-G3 Convertible Car Seat in Onyx

Today: $214.99
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ITEM# 14535387

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ITEM#: 14535387

The Britax Marathon 70-G3 convertible car seat accommodates children rear facing from 5 to 40 pounds and forward facing from 20 to 70 pounds. The seat is engineered to reduce forward movement of the child's head.

  • Rear-facing weight: 5-40 pounds
  • Front-facing weight: 20-70 pounds
  • Base with safecell technology designed to compress in a crash
  • Integrated steel bars strengthen connection to vehicle and reduce forward flexing during crash
  • Staged-release tether webbing slows forward movement
  • Side impact protection lined with energy-absorbing EPP foam distributes crash forces, shields from vehicle intrusion and contains child
  • Tangle-free, 5-point harness distributes crash forces across the strongest parts of the body and provides secure fit
  • Harness Ultra Guard System provides resistance to forward movement in crash
  • 70-pound weight capacity for safety and comfort as child grows
  • Rear and forward facing recline for child comfort and positioning
  • High density comfort foam provides extra layer of padding
  • Plush, easy-remove cover provides extra comfort and easy cleaning
  • Two buckle positions
  • Quick-adjust, no-rethread harness
  • Premium lower latch connectors for quick and simple installation featuring push button for easy release
  • Built-in lock-offs ensure snug lap and shoulder belt installation with minimal effort
  • Anti-slip, contoured base grips and protects vehicle seat while offering optimum vehicle fit
  • Harness holders keep harness straps pulled to sides when placing child in car seat
  • Dimensions: 26 inches high x 18.5 inches wide x 21 inches deep


Dimensions 21 x 18.5 x 26 inches
Warranty 1 year Limited Manufacturer
Materials Plastic, Foam
Model Number E9LJ51A

Product Reviews

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  • great product

    got this baby chair on time, it is great, easy to install in my van, my 10 month old baby loves it. He always cries when he sat in his old infant car seat, but with this one he does not cries any more. and he also can sleep well in this car seat.

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  • Sturdy

    It was a little bulky/confusing from the manual to put together initially. This was our first convertible carseat purchase. I do not regret it. It feels very sturdy and the gripping base is a nice feature. I can't really say that the harnesses stay out the the sides while placing child in carseat but that is not a big deal to me b/c our infant carseat is the same. I love how you do not have to remove things to get the harness at the correct level at or below the shoulders. I was hoping it would give us a little more room than our chicco infant carseat but it does not. It is the same and that is not a deal breaker. We feel very confident with this purchase!

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Questions & Answers

Get your product questions answered right here.
  • Can the seat be used if the car does not have anchors?

    • Yes you would just buckle this in to the car. It would be alot safer if this was used with anchors.

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Standard Return Policy:

Items must be returned in new or unused condition and contain all original materials included with the shipment. More Details

FINAL SALE EXCLUSION: Items marked as FINAL SALE are not returnable unless the problem you experience is the result of our error.

Shipping Information:

Our standard shipping method is ground shipping. We also offer expedited shipping for most items. Your final shipping cost and estimated delivery timeframe will be available at checkout.
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** Most Oversize orders are delivered within 1-4 weeks. Some orders may take 6 weeks to be delivered.

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