The following is a summarised version of a paper written on research into two potential reference methods for a NIR fibre maturity and fineness instrument being developed at the United States Department of Agriculture's (USDA) Southern Regional Research Center (SRRC). The objective of the research was to compare values of perimeter and wall thickness derived from the values given by two instruments; the Shirley Micromat and the Zellweger Uster Advanced Fibre Information Systems Fineness and Maturity Module (AFIS F&M). The aim was to choose one of the instruments as a reference method for calibrating NIR spectroscopy. Comparisons were made on the level of error associated with each method and the degree to which data from each method conformed with theoretical relationships.