D.O.T. Women's Motorcycle Half Helmet with Roses (Size M, MD, Medium) Helmet Meets and Exceeds D.O.T. Safety Standards. The Smallest D.O.T. 1/2 Shell Helmet Ever Made. Moisture Wicking Fabric Keeps Your Head Cooler and More Comfortable..Nylon Y-Strap D-Ring Retention System With Sliding Adjuster. Custom Designed Helmet, Available Without Visor Only, Clear Lacquer Finish, Nickel Plated Rolled Tubular Steel Rivets. Free Cloth Draw String Helmet Bag. Free Black Mesh Headwrap How to measure for a motorcycle helmet. Use a fabric tape measure and measure the distance around your head just above your eyebrows. Then select a size from these options, all sizes in inches . - 3XS 17 1/8" - 18" / 2XS 18 1/8" - 19" / XS 19 1/8" - 20" / SM 20 1/8" - 21" / MD 21 1/8" - 22" / LG 22 1/8" - 23" / XL 23 1/8" - 24" / 2XL 24 1/8" - 25" / 3XL 25 1/8" - 26" / 4XL 26 1/8" - 27"