Fresnel Lens, Diameter 200mm (7.9''), Focal Length 100mm, Acrylic Lens (not Glass), for Physics Classroom, Solar Heating, Magnifiying. (Focal Length 100mm)

I used it to light a couple pieces of cardboard on fire it worked pretty well! But having to look at the bright blinding dot kind of sucks. Ive been trying to find something to fix that problem my sunglasses did not work. I want to try a pair of eclipse glasses.

You can't tell from the images, but it's not flat like other Fresnel Lenses I've used. It is covered in circular machining (?) ridges on one side. I'm guessing this design or poor machining is what results in the lens having a terrible focal point completely useless for starting fires on tinder. I would give it 1 star but am assuming amazon lied to me in my search and/or there are variations in Fresnel Lenses that I am unaware of.They've since updated their images to show the ridging. Apparently it is a valid design. With that said, I could not get it to focus how the pictures showed with clear sun overhead. For comparison, my wallet sized Fresnel Lens produced a better focal point so the 3 stars stand.

Only half the circle shows a visable magnafication.I got this to view my huge wall map when desiredbut only the center shows an image, the outeredge all the way around just shows a blur.I estimate half the viewability realestate is lost.Probably better for starting camp fires.