This ingenious wooden tool determines your yarn's "weight," or thickness, by counting the number of times the yarn can be wrapped in adjacent rows around the tool. The Knit-Kard included in the kit then identifies the yarn weight using the WPI number. You can also read the full description or view all Nancy's Knit Knacks WPI Tool Kit.
Now I do not have to wonder if its really lace yarn and not fingering. I know your suppose to swatch, but I would like to do it with the right kind of yarn. Worth the money in my book. Ive heard of wrapping yarn around pencils etc. but I really dont want to trust that. I think its going to pay for itself in the long run.