Western Optical 10x Scale Loupe Magnifier is a great value! Fine scale loupe with focusing ring. The metric scale has a 10mm range in one fifth millimeter increments. The WO-337 10x Scale Loupe Magnifier has a 24mm eye piece. Supplied gift boxed. This instrument is indispensable for RGP contact lens manufacturing and modification. However, it has many other potential applictions for very fine measuring.