NOTE: We strongly recommend ordering one size up from the recommended size on the size chart!Super lightweight weighing only 325-350 grams provides a smart layer of defense against the common surfing head injuries. The Gath Hat's unique helmet shape and expandable neoprene headband automatically adjusts to your head shape for a superior comfortable snug fit, total peripheral vision, and helps provide a comfortable seal to the wearer's forehead minimizing water flow over the eyes.Technical Information: Gath helmets are made from quality materials to strict specifications and are built to last and are backed by a 3-year warranty. All materials are strong, durable, rust proof and will withstand harsh climate conditions and temperature extremes.Shell – Long lasting, UV stable, high impact resistant plastic.Visors – Top quality UV stable, shatter proof plastic.Peaks – UV stable, shatter proof, flexible, durable plastic.Liner – Multi impact, non-water absorbent foam.Headband – 10mm thick Multi impact, non-water absorbent foam.Comfort Strips – Multi impact, non-water absorbent foam.Fittings – All Gath helmet custom built screws and rivets are made from strong non-corrosive, salt water resistant materials.SIZING:Small:Head 21 1/4" to 21 7/8" | 540mm - 555mmAmerican Hat: 6 3/4 to 7Medium:Head 22" to 22 5/8" | 560mm - 575mmAmerican Hat: 7 to 7 1/4Large:Head 22 7/8" to 23 1/4" | 580mm - 590mmAmerican Hat: 7 1/4 to 7 3/8X-Large:Head 23 3/8" to 24" | 595mm - 610mmAmerican Hat: 7 3/8 to 7 5/82X-Large:Head 24" to 24 3/8" | 610mm - 620mmAmerican Hat: 7 3/4 to 7 7/83X-Large:Head 24 3/8" to 24 7/8" | 620mm - 630mmAmerican Hat: 7 7/8 to 8