je pense qu'il s'agit de:

dual or double-ring spun denim

ring spinning = filature à anneaux
mais dual ou double spun pour la qualité du tissu signifie dire que trame (fil vertical) et chaîne (fil horizontal) sont en filé pas uniquement la trame comme sur la plupart des denims moins resistant

ring-spinning = filature à anneaux (retordage)

Open end spinning - bouts libres san retordage - moins résitant


Single Ring Spun Denim
This is the denim of the past. Ring spun denim is more rugged and is a less refined yarn. This yarn adds character to the denim because of the "slubs" running throughout the yarn. Slubs are tiny knots of cotton, and are found randomly throughout the yarn. Most Ring Spun Denims are woven with Ring Spun yarns running lengthwise and Open End yarns running widthwise, this is called a Single Ring Spun Denim. A Double Ring Spun Denim is made with pure ring spun yarns woven into the length and the width of the weave.

Double Ring Spun Denim
A denim's weave has yarn running both lengthwise and widthwise. Most Ring Spun Denims are woven with Ring Spun yarns running lengthwise and Open End yarns running widthwise, this is called a Single Ring Spun Denim. A Double Ring Spun Denim is made with pure ring spun yarns woven into the length and the width of the weave. Our Cheyenne, Duster and Stretch fabrics are Double Ring Spun denims.