This needle sizer is the perfect compact tool. You can check your needle size, check your gauge, and measure your stitches or rows all with this pocket-sized tool. The Knit Picks view sizer can check the gauge of every size of Knit Picks needle, from US size 0 (2 mm) to US size 17 (12 mm). There is also a six-inch ruler, and a magnifying section to measure your gauge.