There are two sizes: Black M size: Length 21.5CM, Width 17.3CM; L size: Length 22.5CM, Width 18CM. Please specify your desired size when ordering. Infinity is a revolutionary aero road helmet developed in collaboration with Team SKY, achieving both breathability and aerodynamic efficiency. Its most prominent feature is the movable air vent cover on the top of the helmet, which can be opened and closed with one hand. The ultra-lightweight adjustment system "OCTO FIT" is ergonomically designed to provide a perfect fit for any head shape.