When looking for a HELMET
I suggest a 'double impact' helmet for roller derby (not the strofoam lined ones) the 'single impact' ones with the squishy pads. Why you ask? The harder lined styrofoam helmets offer no protection after the first hit, however, it will offer more protection than a 'single impact' on that first hit to the head.
A 'double impact' helmet offers greater protection over time than the 'single impact' helmet.
My suggestion, S-ONE! Most comfortable, quality foam linings, variety of colors and styles,.. I've taken a couple blows to the head on this brand and have suffered NO concussion.