Red Mutiny II Helmet
Great helmet! Low profile design and you can wear a beanie and goggles underneath if you want to be extra steezy while still protecting your head.
My head measures 22.5" around the part where a hat would sit. The medium size fits me great.
And you can add audio to this helmet (and any RED helmet). You just have to buy either the Redphones or Redphones Premium DJ Headset.