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.
Indicates there is no data in the hmirs and the nsn is in a fsc not generally suspected of containing hazardous materials.
Precious metal content is unknown
The item does not have a nuclear hardened feature or any other critical feature such as tolerance, fit restriction or application.
HMIC: Hazardous Material Indicator Code. A one position code that identifies a hazardous item.
PMIC: Precious Metal Indicator Code. A one position code which identifies items that have precious metals as part of their content. precious metals are those metals generally considered to be uncommon, highly valuable, and relatively superior in certain properties such as resistance to corrosion and electrical conductivity.
ESD: Electrostatic Discharge. Indicates if an item is susceptible to electrostatic discharge or electromagnetic interference damage. electrostatic discharge damage occurs when an accumulation of static electricity generated by the relative motion or separation of materials is released to another item by direct contact. electromagnetic interference damage occurs when an item comes into proximity with an electrostatic or magnetic field.
ENAC: Enviromental Attribute Code. Identifies items with environmentally preferred characteristics.
CRITL: Criticality Indicator Code. Indicates an item is technically critical by tolerance, fit, application, nuclear hardness properties, or other characteristics.