1.1 This test method covers the estimation of the average fiber diameter of wool fibers by use of the Port-Ar and the WIRA Fiber Fineness Meter instrument, which operate on the air-flow principle. Other air-flow instruments have not been tested with this method. The method is directly applicable to non-medullated, carded wool and wool top. 1.2 This test method is applicable to grease wool and scoured wool after the samples of such materials have been prepared as directed in Test Method D2130. Note 1: The use of the Micronaire instrument for measuring the fineness of cotton fibers is covered in Test Method D1448.  The assignment of grade for wool and mohair is covered in Specifications D3991 and D3992. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.