This 17inch parallel ruler ensuring stability and accuracy in measuring distances and angles on Chart Perfectly suited for chart plotting, route planning, and maritimes navigation training, this tool is essential for any serious seafarer For professional, captains, enthusiasts, and maritimes students seek navigation tool precise marine navigation with the Marine Navigation Parallel Ruler, featuring arm for durability Enhances your navigational skills with this expertly crafted instrument, to withstands the rigor of sea voyages while providing clear scale marking for easy use, Manufacturer: LiRRvb