A right angle ruler with indented markings. Measures three inches left and right of the vertical axis and measures three inches vertically. The full size of the ruler is about 6.5x4 inches.This is best 3D printed with 0.2mm layer thickness. The plastic shrinks when it cools so if you need the markings to be precise the stl file must be scaled up to compensate before slicing. For ABS, scale by 100.78%.