Triangular ruler, compass divider required for first class nautical chart issues. Smaller sizes may not be able to draw. If you are studying the nautical map problem of first class small vessels, then you can rest assured that the "Small Ship Exam Nautical Drawing Set" is a breeze. Set Contents: 1 x triangular ruler with red line 11.8 inches (30 cm) x 1 x triangular ruler for fixing 8.3 inches (21.2 cm) x 1 x Maximum radius of 4.3 inches (11 cm) x 1 x divider total length 4.7 inches (12 cm) x 1 x practice chart (W150 x W20 x W20 x W2