Brass Round Edge Ruler Set of 5: 6, 10, 12, 18, and 22mm diameters. - Brand: Craft Sha - Model Name: UNBLOWN - Sizes: 6, 10, 12, 18, and 22mm diameters - Set Contents: Set of 5 This ruler allows you to draw lines at a consistent width along a pattern using a silver pen or similar. It's convenient when you want to draw a line in addition to the sewing line. The circular part is 3mm thick and has a 1mm thick lower edge, making it less likely to slip off the pattern during work.