XIANQI High Quality This architect ruler is made of anodized aluminum alloy, solid and sturdy. Designed for maximum durability, this 3 sided engineering ruler is perfect for long-time use Laser-etched Scale The metric scale ruler with durable laser cut metric prints for accuracy. They will not wipe or scratch off ever Metric Scales3 sides with 6 scales: 1:20, 1:25, 1:50,etc. Ideal for blueprint, professional applications, architecture, civil engineering, drafting and technical illustration(Notice: Make sure it is what you want before placing the order) Precise ScaleThe black scale ruler is professional grade with supreme accuracy, suitable for engineers, professors, hobbyists, manufacturers Safe ToolOur tri-scale ruler was created with your safety in mind. Chamfer edges design, comes with a protective bag, no more accidental pokes, scratches and cuts