Special Features:

Precision photochrome reproduction on 1.0+/- 0.2mm on ground and polished plate glass, line width 10 microns, fits negative or positive eye pieves, spring-wire locking ring offered to secure in other manufacture's eye piece diameter 19 mm

Properties:

An item, usually made of glass, having fine wires or hairs, or etched or printed fine lines on a surface, and placed in the focal plane of an optical instrument to establish a reference point to the axis for the purpose of aiming, measuring, ranging, and the like. Excludes lens, optical instrument.