Pure Silk is a twisted pure silk, popular for traditional fly patterns such as spiders or Clyde style. If you are wanting to use Pure Silk flat simply untwist it by spinning on your bobbin holder. This dual purpose means it can be used in different ways and has added strength compared to traditional silks. Pure Silk has been developed to be a close match to the historic colors of pure silks as seen in the Edmonds & Lee book Brook & River Trouting for which we are lucky enough to have an original copy. Pure Silk has an approximate denier of 250d.