Omnigrid rulers are made of durable acrylic plastic with both yellow and black printing which allows the user to see the grid on both light and dark fabrics. Features a left- and right-handed numbering system and bias lines oriented to the bottom of the ruler. This eliminates the need to flip and turn the ruler to use both sets of diagonal lines. Omnigird rulers are extremely accurate; each ruler is laser cut to within a .002" accuracy. Includes the 2-1/2", 4-1/2", 6-1/2" and 9-1/2" square rulers.