Glass fiber length is of great concern to both the compounder and molder of fiberglass reinforced thermoplastics. We know that the fiber attrition is considerable, but how short is it and where in the process does it occur? Can it be affected by using the longer length chopped strands? These are the types of questions that have gone unanswered because of the considerable time and effort necessary to quantify fiber length and length distributions. Burning the resin off, taking a photomicrograph of the glass, and physically measuring the lengths with a scale takes a great deal of time and money. A second method sometimes employed is a sieve analysis. This involves a series of screens which classify the fiber length by the size of the openings. This method, however, can lead to higher than actual averages due to a matting effect of the longer fibers which sometimes can trap the shorter fibers. Fibers that pass through the screen openings lengthwise can also distort the reported value. There is now available fast and accurate computerized, electronic image analyzing equipment that facilitates fiber length measurement.