Jeweler"s Loupe - Double Power 10X & 20X. New 20X & 10X Chrome Plated Eye Loupe. This is a new dual power loupe made of optical glass with a swing-away, chrome plated case. The shape allows it to rest comfortably in the eye socket. This has become the standard style of loupe used in the watch making industry and is excellent for any application where magnification is needed. It is 10X power on one end and 20X power on the other. The 20X has a 12 mm lens and the 10X has a 18 mm lens. The 10X lens has a focal distance of 1 in. (25 mm) and the 20X lens has a focal distance of 1/2 in. (13 mm)