Specifications:Create fascinating patterns with this classic art tool that has been loved for generations.Traces out the curves turning math into beautiful art.Through different arrange and organization, you can draw a lot of patterns.Put one the the gears in the big circle, then position your pen tip in one of the little hole of the gear, and draw along the gear teeth.Then you can easily draw a lot of amazing patterns.Makes learning math and design fun, suitable to adult and children. Item Name: Mechanical RulerMaterial: PlasticQuantity: 1PcFeatures: Durable, Easy to Use, Professional Tool, TemplateScale: 21cm/8.27", 25cm/9.84" (Approx.)(Optional)Size: 22cm x 13cm/8.66" x 5.12", 26.7cm x 15.2cm/10.51" x 5.98" (Approx.) Notes:Due to the light and screen setting difference, the items color may be slightly different from the pictures.Please allow slight dimension difference due to different manual measurement. Package Includes:1 x Mechanical Ruler