FRESNEL MINI-LENS (Mini C.C. size) Measuring only 3.5'' x 2.25''. These are little gems!
Our Field guide: "ACW pocket survival/life guide" can come with a lens already. These are great and compact back-up resources for reading small things, Fire starting with the sun, signaling , working on small things (tick removal, or tinkering in the field). The larger "full sized" lens can be found here.
The way they work is rather interesting, a Fresnel lens is a type of composite compact lens...
For a video/ field demo of starting a fire with the Fresnel mini lens, check this one out.