Size Chart: Half Dome Helmet men's

HELMET SIZING

  S/M
Size Range 19-22.5 in 48-57 cm
Weight 11.6 oz 330 g
  M/L
Size Range 22-24 in 55-61.5 cm
Weight 12.3 oz 350 g
How to measure:
Head: Measure around the largest part of the head–about one inch above the eyebrows.