They are unique, relatively speaking. Probably several jackets were made of the same fiber - but the chances of another person with the same jacket from the same dye lot are slim to none.<P><b>Fiber Comparison <P>There are four types of fibers. These are<P><BR>Animal - e.g. wool <P><BR>Vegetable - e.g. cotton <P><BR>Mineral - e.g. asbestos <P><BR>Man-made or synthetic - acrylics, nylon and polyester <P><BR>The main characteristic of a fiber used for comparison is color type, diameter, coarseness, the presence of additives and machine marks made during production, changes to the fiber due to the sun or bleaching, or discoloration and cross sectional shape. <P><BR>The most important characteristic for forensic investigators is the color of the fiber. The color is produced by different dyes, and can be determined by an instrument called a microspectrophotometer, which produces a "fingerprint" of the color based on the absorption of light. Identical color fingerprints have a good chance of being the same fibers. <P>Most comparisons of fibers are done on either a compound microscope or a comparison microscope. Every characteristic that is tested for must be the same for a match to be made. This means that even if most characteristics of two fibers seem to be the same, a difference in only one property means that they can not be matched.</b><P><P><BR>