SIZING CHARTDesigned developed after several years of focused efforts and crucial feedback from top world class athletes in. HJC's top engineers went to work and created a race-bred helmet that is truly worthy of top race circuits. The RPHA 1 is the very same model used by HJC's world-class athletes in both MotoGP and. WorldSBK, and HJC is set to finally launch it into full production with FIM homologation (FRHPhe-01) -the safety. The RPHA 1N is the very same model used by HJC's world-class athletes in both MotoGP and WorldSBK, and. HJC is set to finally launch it into full production...