Z-20 Photochromatic - Anti-Fog Dirt ShieldZAMP Z 20 Photochromatic Shield Dirt & Anti Fog Exclusively from Zamp Racing! Photochromatic Dirt Anti Fog Shields. To prevent dirt from packing in between the top of the shield and helmet, these shields utilize rubber trim across the top to help seal the shield tight to the helmet. Go from bright to dark racing conditions without having to change shields! The new Z 20 Photochromatic Anti Fog Shield smoothly transitions from clear prism to red prism,