NOTE: We strongly recommend ordering one size up from the recommended size on the size chart!The GATH GEDI is chosen for water sports requiring a higher level of impact protection. White Water, Wake Boarding, Kite Surfing, Windsurfing and similar sports - PWC (power water craft), Jet Ski, Rescue and Professional activities. Comes with removable Ear protectors, Spare Comfort Strips. chinstrap anti Rash Sleeve and Storage Bag. Available accessories, Peaks and Visor.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