Oneill Hoods Size Chart
  X-Small Small Medium Large X-Large
Head Circumference (in) 20.5-21.5 21.5-22.5 23.5-24.5 25.5-26.5 27.5-28.5

These are general guidelines only, sizes are not guaranteed. But no worries, since at LeisurePro we offer our exclusive PFF Guaranty