The Best Glide ASE Credit Card Fresnel Lens Fire Starter and Magnifier Lenses are a great back up fire starter and will fit practically anywhere. Our Fresnel Lens Fire Starter is small, flat, light and inexpensive. Some practice is required and of course, one needs a sunny day for it to work. We do not recommend the Fresnel Lens as a primary fire starting tool, but as an addition to an already supplied kit. The Fresnel Lens Fire Starter, or Credit Card Magnifier, is so inexpensive why not carry a few just in case. The Best Glide ASE Fresnel Lens Fire Starter is more commonly known as a credit card magnifier. However, our version has 4 power magnification, much more than the 2X or 3X of standard credit card magnifiers, making it a great magnifier fire starter. The Best Glide ASE Fresnel Lens has been used for years in various applications, most notably the Light House Lens. Using a Fresnel Lens allows the light of the light house to be magnified numerous times and still be relatively small. It is a truly amazing invention. The Best Glide ASE Fresnel Lens is made of Optical PVS and is .4mm think and weighs 5.5 grams. In short, it is the size of a very thin credit card. The Fresnel Lens Fire Starter comes with a green, red, or yellow protective case with the Best Glide ASE Logo.Please note: These fresnel lenses are made of Optical PVC. However, there may be trace amounts of Diisononyl Phthalate (DiNP), which may require warning labels pursuant to California's Proposition 65. This labeling is ONLY relevant to CALIFORNIA. Since sellers cannot control which fulfillment center inventory is sent to customers in California vs. Outside of California (where it is not relevant), sellers may label all units in accordance with California's Proposition 65. Thus, customers outside of California may receive fulfillment center inventory with this California Proposition 65 Warning.