Gauge: Knitting needles are US 0-15 and metric 2-10mm. this hole can help you quickly confirm the needle size. WPI Specification: Quickly determine the WPI rating by counting the number of yarn wraps per inch or laying the yarn along the black strip find a match. Convenience: Convex notches are used to fix on the spinner to avoid yarn unraveling. Round hole can be paired with gift chain and lobster clasp, easy to carry or hang anywhere you want. Tool kit: Package contains 3pcs different tools, wraps per inch single tool, yarn spinner gauge, wood multi-functional rulers. Multifunctional: Made of high quality wood, clearly marked and multi-functional, you can quickly determine the needle number, WPI and yarn weight. A perfect multifunctional sewing and knitting tool for everyday life.