Western Optical 15x Scale Loupe Magnifier is a great value! Fine scale loupe with focusing ring. The metric scale has a 14mm range in one tenth millimeter increments. The WO-338 15x Scale Loupe Magnifier has a 19mm eye piece. Supplied gift boxed. This instrument is indispensable for RGP contact lens manufacturing and modification. However, it has many other potential applications for very fine measuring.