Review on 5col Survival Supply's Pack of 4 Credit Card Sized Pocket Magnifier & Firestarter with Fresnel Lens by Cody Bowie

There's nothing special about that. The charred fabric caught fire in about 16 seconds on a sunny day. The dark birch took about 45 seconds. They are lightweight and easy to use. Good lens for survival and bushcraft. They're made out of thin plastic, so they won't take a lot of abuse, but they don't have to. (Note: Don't try running light tinder with solar ignition, it takes a long time and may not work at all. Many beginners make this mistake, blaming the lens. They need dark colors that absorb heat.)