Louis Garneau Men's/Unisex Helmet Size Chart
  Small Medium Large
Hat Size 6frac12;-7 7-7frac38; 7frac38;-7frac34;
Head Circumference (in) 20frac12;-22 22-23frac14; 23frac14;-24frac38;
Head Circumference (cm) 52-56 56-59 59-62

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