These make a great back-up fire starter for sunny days. Carry in your wallet and use it to conserve or firesteel. With a little technique you can use this to ignite your tinder bundle. Be sure to practice this skill before ending up in a situation where you need to rely on it! They're also great for your daily magnification needs, like reading the menu in a dark restaurant. These flexible, credit card-sized lenses magnify up to 4x and are perfect for wallet or pocket carry. Can be used for everyday magnification needs, like reading menus and newspapers. On a sunny day these fresnel lenses can be used as backup firestarters, saving you a match or a strike on your ferro rod. Protective Sleeve is printed with the Survival Mnemonic from Military Field Manual FM 21-76-1.