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.