Alvin 450 proportional dividers are used for dividing lines or circumference of circles into a number of equal parts and for enlarging and reducing lengths in different ratios. With a simple adjustment, reductions or enlargements can be transferred from original scale drawings with exacting accuracy (+ 0.1mm for any ratio). 7-1/2" divider, graduated for lines and circles. Has adjustable, replaceable steel needle points. Alvin Duraluminum proportional dividers are quality-made in Germany.