I have an Arai Quantum, I recall being told the RX7 was a different shape to the Quantum (for the European market models, incidentally Arai tells us the shapes can vary across different geographical markets, for the same helmet model!!??). The info was the RX7 was more straight & narrow, and the quantum more rounded, if you catch my drift.

I'm not sure what the latest Arai model is just below the RX7, but this could be again a slightly different shape, could be worth checking for someone with a non-RX7 shaped head.

My Quantum is a Cadalora Rep, so many years old now. The Arai marketing spiel says you should replace a helmet every 4 to 5 years.

Has anyone ever found their top quality Arai to suddenly reach its sell-by date, and break in half in the event of an impact????

It looks like AGV are producing some high quality lids now, I never considered Shoei because of that seat-belt type chin strap, have they gone to a Double D ring yet??
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30