In case anyone reads this and gets excited enough to buy one, realize fresnel lenses are actually dangerous.<p>It&#x27;s almost like keeping some turpentine soaked rags in a cardboard box. Sort of kidding. The point is, you can have the lense somewhere you think is safe, but the angle of the sun changes throughout the year and one day six months later rays of light hit it. Or you have kids that don&#x27;t think that way, and they leave it somewhere.<p>Even as a fully aware adult, it&#x27;s counterintuitive, because you&#x27;ll be trying to take it outside and accidentally burn yourself, or set it agains something while you&#x27;re getting ready, not realizing the lens was born ready and doesn&#x27;t care about your plans. You always have to carry them in a sheathing material. Your brain expects something like that to have an off switch.<p>They&#x27;re cool, but you should probably keep them in an opaque sheath in a gun safe, and leave it alone when you&#x27;re drinking.