Fresnel Lens Large, 300x300mm, Focal Length 510mm, Acrylic Lens (not Glass), Olar Death ray for Physics Classroom, Magnifiying Sheet Fire Starter for Solar Heating, Solar Oven.

Apologies to the seller who asked me to review this... took months... I wasn't really sure which project I was going to do with it.Let me tell you, this REALLY works. It works well as a large magnifier and it REALLY works well at focusing a light source.If you use this for emergency fire starting (or just cuz you never grew out of your light-things-on-fire-with-a-magnifying-glass phase) just be warned: IF NOT USED PROPERLY, THIS IS VERY DANGEROUS! I tested this by focusing it on a small piece of cardboard... just using the ambient sunlight on an autumn day (and this was inside my screen room, so the fun was being filtered by screen) the cardboard ignited in SECONDS. Paper ignited almost immediately. WEAR HEAVY DARK SAFETY GLASSES OR DO NOT LOOK DIRECTLY AT THE FOCUSED LIGHT SPOT. And MOST DEFINITELY do not leave this anyplace where sunlight could go through it and focus on anything even remotely flammable. Do not walk with it hanging at your side... if it stops for 1 second with the bean focused on your leg or pants, you will regret it!So, warnings aside, if you have a project that needs a large but light, thin, high-quality lens, this does exactly what it's supposed to do... very well. Just don't blame me if you light your face on fire.