Special Features:

Spacer-no. 4, eyepiece; black; 4 slots 0.060 in. Wide by 0.050 in. Deep; each end contains 2 equally spaced slots; 45 degrees between the opposite end slots; establish length by measuring separation between reference sphere 1.275 in. Radius and surface b (reference radius located 0.065 in. From edge b)

Properties:

A tubular shaped item designed to maintain a predetermined distance between optical elements, such as lenses, reticles, and the like. The bore may be straight, tapered or counterbored, and may have annular serrations to converge or diverge light rays. The surfaces, which mate with the optics, are usually chamfered, concave, and/or have a specified finish designation in the range of 1 to 125 microinches arithmetical average (aa). See also spacer, sleeve and cell, optical element.