Swatch Ruler & Needle Gauge from Clover, a tool for knitters and crocheters. 

A multi-purpose tool for knitting and crochet. Measure your crochet hook or knitting needle size in US, metric and Japanese standard sizes. The Swatch Ruler allows you to isolate a section of your work to easily count both stitches and rows.

How to use

Place the shaft of your crochet hook in the groove that best fits to check your hook size
Place the point of your knitting needle in the hole that fits best to check your needle size
Get an accurate stitch gauge measurement with the 4in (10cm) gauge rulers

Includes

Knitting Needle Gauge
Crochet Hook Gauge
Swatch Ruler