If you're looking to reduce the amount of fog in your snowmobiling helmet or would like to upgrade from a street helmet then check out the Vega Replacement Dual Lens Snow Shield. It fits most Vega model helmets and is easy to swap out.
Dual lens Lexan™ snow shield decreases fogging while snowmobiling
Series A shields fit Vega Altura, Mach 2.0 Jr, and Summit 2 helmets
Series B shields fit Vega Insight, and Summit 3 series helmets