Louis Garneau Vorttice Helmet
This TT lid is awesome! It has a nice amount of air flow, and fits great. There is plenty of adjustment with the Spiderlock SL fit system. It can be worn with or without the attachable lens, and Louis Garneau has designed the helmet to be equally aerodynamic either way (unlike some competitor's helmets that depend on the lens).
The helmet is also unique in it's design with the cut-off rear. This makes the helmet more aero in cross-winds and if your head is tilted down looking at your computer (or suffering).