The RBK 8K is the first fully customizable helmet and is also the lightest helmet for elite players. No tool needed to adjust - Slide the FITCLIP up, adjust the length of the helmet, slide the FITCLIP down. That's all there is too it. Rear MICRODIAL adjusts circumference by tightening the Stabilizer straps for a true customized snug 360° fit Molded grip texture Comfort Cushions deliver snug pillowy comfort Mechanically attached EPP liner delivers pro-proven protection and integrated venting channels keep your head cool Composite SUBSHELL is lightweight and stiff MAXVENTS venting throughout the helmet keeps the player cool, saving precious energy for the game Translucent SURLYN ear covers protect and blend with the look of the helmet - Ear covers are removable Secure-strap ear loops keep the chin strap in position Zinc plated flat/star screws minimize rust. Screwdriver and dime friendly CSA, HECC and CE certified Features 3 unique shell sizes (S, M, L) for an anthropometrically optimized fit 10 colors to choose from Sizes: hat size (head circumference): Small 6 3/8 - 7 (20-22") Medium 6 7/8 - 7 3/8" (21.5-23") Large 7 1/4 - 7 7/8" (22.8-25") XL 7 5/8" - 8" (23.5-25.22")