Durable plastic needle gauges and rulers:
Rectangular model has both imperial and metric rulers (5" and 13 cm) and measures knitting needles from US 000 to US 15 (1.5 mm to 10 mm) and crochet hooks from size E through N.
Square model is double-sided, with imperial rulers and US needle sizes on one side and metric rulers and mm needle sizes on the other. Use the cutouts to measure your stitch and row gauge over 2" or 5 cm, and size needles from US 2 through 15 or 2.75 mm through 10 mm.