This is the best WIP tool ever! The drag about checking WPI is that it's difficult to maintain perfect tension as you wrap, not to untwist your yarn as you wrap, and to wrap consistently every single time--and any of these errors can make your wip count useless. With this little baby, you just pull your yarn taut, line up the transparent gauge over your yarn until you find the best match, and presto! Gauge! I typically take a reading over several spots in a draw's worth of yarn (a foot or two) and pick either the average or median reading.
Instead of stopping everything and unwinding your yarn and wrapping it (which can be a lot of wraps on a fine yarn) and wondering if you wrapped it just as tightly/loosely last time, you just stop, measure, and go on with your spinning. You can also let the yarn ply on itself to to an equally quick check of your finished gauge. Brilliant!
Plus! It comes attached to a clip for your spinning bag with an 18-inch retractable cord, so you can always keep it securely attached where it needs to be. If you don't use a spinning bag, just tie a ribbon around your wheel and attach it to that.
Comes packed on a bagged hang card with instructions, including a chart translating wip to knitting gauge.
Have any questions? Contact the shop owner.