A Holding length, start-of-scan and crimp cause a shortening of the determined mean and upper-half-mean lengths by both the Spinlab and the Motion Control HVI. The initial point of measurement for both HVIs occurs at approximately the same position. The Motion Control HVI determines the mean length by weight which is longer than the mean length by number determined by the Spinlab HVI. Motion Control indicates a start of measurement at 0.20 in. while Spinlab starts its measurement at 0.15 in. Similar lengths measured on the Motion Control must then be 0.05 in. longer than those measured on the Spinlab HVI as long as there are no adjustments in the data. Specimens presented to each of the instruments differ from the theoretical as well as from each other. Fiber length distributions by weight which would present the specimens to either instrument are compared with each other as well as with arrays.