There are 3 gauge scale rulers available; Green for fine and standard gauge knitting, Yellow for mid gauge knitting and Blue for chunky gauge knitting.

This scale is designed to show how many stitches and rows per 10cm, measuring between yarn markers on the tension swatch.
The scale has two sides. The side with the large "S" at the left edge is used for measuring stitches, and the side with the large "R" is used for measuring rows.

This is a new yellow gauge scale.