I'm a maintenance electrician and sometimes need to read tiny serial numbers in dark dirty places, or the color code of a resistor or some other value or rating that is difficult to accurately read with the naked eye, and for the past six months I have found that this wallet lens to be the perfect solution. Outside of magnifying small text, I have even used this to start a fire.
The pocket Fresnel makes a brilliant addition to my kit of tools at my job but also is a useful survival tool when I'm outdoors. It fits in my wallet which I'm never without. Even when my kids play with my keys and I can't find them afterwards (or use the tools on my keyring) I know I've still got one tool tucked away. Best part of this lightweight super practical EDC? It's super cheap! I got mine in a 6-pack from Lee Valley, but you can get similar ones elsewhere online.