100 euro for one on a Lazer helmet. PERFECT. In the dark it is almost 100% clear, in strong sunlight it is dark enough to make my eyes feel easy, OK. Never gets too dark, but it works. It takes some 15 seconds from totally dark to totally see through, so I take it slow when enering tunnels on a sunny day.
Beats drop down shades-visors, dark visors etc. For me perfect... except for the price.