4241-1 Size: 18" Features: -Extremely durable and impervious to most solvents. -Calibrated in inches centimeters pica and points. -Precision-made of anodized silver-colored aluminum with a hard tempered blade and an ultra smooth surface. -Overall Thickness: 0.12 Millimeters. Product Type: -Drafting Supplies. Dimensions: Size 12" - Overall Width - Side to Side: -12 Inches. Size 18" - Overall Width - Side to Side: -18 Inches. Size 24" - Overall Height - Top to Bottom: -1.25 Inches. Size 24" - Overall Width - Side to Side: -24 Inches.