Using TeXtreme Spread Tow carbon fibre reinforcements in the shell, the TLD D4 Carbon Freedom helmet has helped reduce down the weight of the full face helmet by almost 50 grams without sacrificing strength. Despite the loss in weight, Troy Lee were able to strategically add EPS (expanded polystyrene) to increase strength and durability. The integrated MIPS (multi-directional impact protection system) brain protection system designed to reduce rotational motion transferred to the brain from angled impacts to the head. The D4 package is rounded out with lightweight titanium D-rings, collarbone suspension system and quick release XT2 3D cheek pads and X-Static washable liner. Size Guide: X Small = 20.8-21.2\" (53cm-54cm) Small = 21.6-22\" (55cm-56cm) Medium = 22.4\"-22.8\" (57cm-58cm) Large = 22.8\"-23.2\" (58cm-59cm) X Large = 23.6\"-24\" (60cm-61cm) XX Large = 24.4\"-24.8\" (62cm-63cm)