The TV-15 5-15x TriView Industrial Magnifier from Carson Optical offers you a choice of magnifications factors. Each of the three lenses is 5x. Combine two and you get 10x. Combine all three and you get 15x. When mot needed, it folds neatly into its own pouch.
Each lens contains 5x magnification
Combine two lenses together to make 10x magnification, or three to make 15x