Crystals And Leaves Bound To A Yarn Hank With Stars Spinners Control Tool, Wpi (Wraps Per Inch) Ruler Made From Cherry Wood For Yarn Gauge Crystals and leaves are bound to a yarn hank spinner control tool, with stars floating above. This WPI (Wraps per Inch) Ruler is made from cherry wood and is used to identify the gauge of a yarn. This is great for any who loves yarn skeins and crystals. Wraps per inch (WPI) is a way to measure the thickness of a yarn. This tool is used by spinners but is also helpful for knitters and crocheters to determine the weight of the yarn and what the approximate gauge will be. This guide also has lines on the back to measure your yarn against, including lace, fingering, sport, DK, worsted, bulky, and super bulky. This yarn guide measures about 3 inches tall by 1.5 inches wide and comes with a brass clasp to hang on your knitting bag. Since each piece of wood is unique, the item you receive may be slightly different from the photos.