I just make sure there is alot of foam, and fits in my helmet nicely, and fits on my face nicely. I use steelmx and really like them. Their chrome lenses scratch pretty easily but clear is good.
http://steelmx.com/moto/index.html check them out.
"Jump for show, Corner for dough"
"In ball and stick sports they give you the balls, In Motocross you have to bring your own"
Sponsors:
Glens Sport Center, FC MODS, MSR, Sunline, Tag, Filtron, Six Six One, Steel Mx, Dunlop,