What are the differences between the Britax Marathon, Britax Decathlon, and Britax Boulevard?


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Questions asking about the differences between the three Britax high-weight harnessed (HWH) seats (Boulevard, Decathlon, and Marathon) seem to come up fairly often.

Here are the major similarities and differences:

All three seats have a harness weight limit of 65 pounds.
All three seats are basically the same shell.
All three seats have a FF tether and a RF tether.
All three seats have HUGS for use when FF (you can use them RF, but they are not required).

~ The Marathon is a basic (but AWESOME) seat with four sets of harness slots (the highest is around 16.75-17").
~ The Marathon has a lever harness adjuster (as opposed to push button) and has bars to which the LATCH straps are attached.

~ The Decathlon is a lot like the Marathon, but has more infant padding and three crotch strap positions (the Marathon and Boulevard only have one).
~ The Decathlon has a push-button harness adjuster (for loosening the harness) and does NOT have bars to which the LATCH straps are attached.

~ The Boulevard is the most different. It has infinite harness heights (there are knobs to adjust the harness height) and wings that supposedly add total side impact protection.
~ The Boulevard has a lever harness tension adjuster and has bars to which the LATCH straps are attached.

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