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The John T. Riddell company developed and patented the first plastic helmet
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Invention of the first chin strap
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The single face bar was added to plastic helmets
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First appearance of the radio helmet, introduced by the Cleveland Browns
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Riddell adds air bladders inside helmets to soften impact
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Full face mask appears
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First appearance of protective visors
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First polycarbonate helmet
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Single bar helmets formally banned by the NFL
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Impact indicator chin strap launches, designed to identify head injury