I have used these for so long I cannot remember when I bought my first one. What I do know is that I began with a two power, went through the four power you see here and now need to use a ten power. When you study knives you need magnification. The four power focuses about eight inches from your eyes. Visor light sold separately.
OptiVISOR® #5 - 2.5X power @ 8"
Low stock, call for availability
OptiVISOR® #10 - 3.5X power @ 4"