The Aeroshell Z1 is a transparent plastic cover, designed to fit perfectly over the Z1 and Z1 MIPS models of Lazer helmets. The AeroShell snaps into place and protects your head from cold wind and precipitation while still allowing for some air movement under the front of the helmet and out of the rear vents. The AeroShell is nice in that it gives you the benefits of a closed helmet when needed and it's easily removed when riding conditions are such that additional ventilation is desired. Snap it on when the rain is coming down and pull it off when the sun starts to shine. Alternatively, the Aeroshell provides a significant increase in aerodynamic performance when it's installed on the helmet. By closing off the ventilation holes, the amount of drag is greatly reduced, resulting in a faster ride. Please note that this particular version only fits the Zq model, is size specific (Small, Medium, and Large), and comes in the color Transparent.