These flexible, credit card-sized fresnel lenses magnify up to 4x and The lightest weight fire starting option on a sunny day!
Carry one in your wallet and use it to conserve matches 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.