This is a snap-on visor for open-face helmets. My dealer recommended this product to me when I was looking for a visor for my Shoei RJ-Air helmet. I've been riding without any visor with this helmet and needed something to keep my eyes from drying out (and picking up road gunk) even with my CB #2 -2" w/wings. It will fit any three-snap helmet (the snaps are adjustable sideways).
I picked up the product today and went for a ride this evening. I like it a lot, and at $26.95 it's worth twice as much or more. I had one of those cheapie ratching up/down visors. This one is infinitely adjutable, is very smooth, the visor is made of 2 layers of plastic for anti-fogging (don't know yet if it's acrylic, polycarbonate, or depleted plutonium), and when it is slid up away from you it cleverly slides up over the top/front of the helmet -- in other words, it doesn't just flip out in front of your face. This works nicely if your passenger wears this -- he/she won't ram it into the back of your helmet during a sudden stop.
Seer also makes a lot of law enforcement helmets and related products, and has a line of custom hand-made and hand-painted helmets. This may be the same company that David Shealey (I think) mentioned when we had a discussion of LEO look-alike RT-Ps and riding gear.
In use going down the road with the windshield all the way down there is a good bit of noise generated by wind going through the slide mechanism; putting the shield up a couple of inches takes it right away. With this visor I can now ride looking over the shield as I prefer to do, and as do all you who ride with full-face helmets.
Nice product, and I'd buy it again. See www.superseer.com