An essential drawing tool for any serious drafting student and professional architect or engineer, the Acu-Arc adjustable ruler is the one instrument that does it all. No more expensive beam compasses or pre-packaged curve sets that limit you to the given sizes. With this ingenious easily-adjustable design, the possibilities are nearly limitless. Select your choice of measurement in inches or centimeters for this amazing and affordable instrument. A ruler that eliminates the need for a beam compass or expensive curve sets . Can be adjusted to any radius, from 7.88 in. to 200 in. (17 cm. to 500 cm.) . Can be used to determine the radius of an existing curve for dimension drawings . Find center lines & center points or determine what a curve must be to fair in existing points or lines on a drawing . Marked in inches or Centimeters