Made of sturdy resin, the Swatch/Needle Gauge by ChiaoGoo is a multi-purpose tool which helps determine gauge on one hand, and measures your needle/hook sizes on the other hand.
 
To use it as a swatch gauge, simply place the tool on your swatch and count how many stitches/rows fit inside the cut-outs (along the bottom for stitch gauge and up the side for row gauge).
 
Printed on both sides are handy conversion charts, as well as yarn standards tables for reference. The tool is double-sided for US/metric and knitting/crochet differentiation, making it a valuable addition to your notions pouch or your project bag. 
 
Measures approximately 14 cm x 14 cm.