Summary

About 1.5X magnification. 2mm thick, A4 size (180 X 210mm).

The 'lenses' are cut into the plastic as micro-grooves (very clever), as invented by Augustin-Jean Fresnel (pronounced "Fren-nel") in about 1818, and originally used as the 'magnifiers' around the lights of lighthouses. To use a Fresnel magnifier you must hold it a few inches above the object, they do not work by resting on top of the object.

Read all about magnification and how to choose a magnifier,

Technical

Magnification / lens size in mm: about 1.5X, A4-size.

Field of view: a double page of a paperback book

Lens material: plastic

Origin / brand: I bought these as a 'job lot', manufacturer unknown. .

Presentation: it comes wrapped in cellophane.

Applications / Quality

Generally, these are flat (well, not 100% two-dimensional, but quite thin), the largest have a huge field of view. .

Specifically, what this lacks in optical quality it gains in sheer size, enabling you to see one large page at a time (or the double page of an open paperback book).

Alternatives

Conventional reading magnifiers with handles are better in optical quality And small (pocket-size) general purpose folding magnifiers are more powerful.