Omnigrid Marking Ruler Trio are made from a durable premium quality plastic and laser cut for a smooth edge that allows for easier deeper cutting of fabric layers. Designed for left or right handed use. Use these rulers to quickly and accurately perform a variety of marking tasks. Center line is exactly 1/4 from both edges of the ruler. Do not use with rotary cutter knives or other cutting instruments. Rulers are designed for marking only. Includes 4, 6 and 12 rulers.