450mm Marine Parallel Ruler for GPS Plotting & Nautical Navigation - Boat Chart Measuring Tool [Features] The manual ruler provides accurate measurements through the aluminum chain, providing appropriate tension for drawing straight line parallel to another line or reference points. Good Transparency: This parallel navigation ruler has good transparency, does not cover too much information, and can view the entire page. Accurate Scale: The measuring ruler has an accurate scale and is easy to recognize, making it a good accessory for drawing and measuring. A manual ruler provides accurate measurement through an aluminum chain, providing appropriate tension for drawing a straight line parallel to another line or reference point. Easy to Draw: Our nautical ruler is adjusted through stable aluminum chains, which are smooth and powerful, making it easy to draw reference parallel lines. Size Information: This ruler is approximately 45cm/17.72in long and is very suitable for charting. [product information] product name: parallel ruler color: Transparent Material: Acrylic size:450mm Packing list (you can get after purchasing one item): Parallel ruler *1 Please understand: 1. Due to the long shipping time, the item may be damaged during the shipping process, if the item is damaged, please leave us a message through the official website immediately before posting comments, and I will solve the problem for you. 2. Due to manual measurement, the size may have an error of 1-3cm. 3. Colors may vary from monitor to monitor.