Nancy's Knit Knacks WPI (Wraps Per Inch) Tool Kit Made from birch hardwood with an oil finish Measures 5" in length x 5/16" diameter (yarn guide knob measures 5/8") All markings are laser etched into the wood and will not wear off There are markings for up to 3 inches which allows you to calculate a more accurate average WPI on certain hairy yarns A special WPI Knit-Kard comes bundled with the tool in a ziplock bag. The Kard tells the user how to use the tool and provides a useful WPI chart for 6 different weights of yarn