ACU-ARC adjustable curve rulers can be adjusted to any radius, from 6-3/8" to 200" (17cm to 500cm), to determine the radius of an existing curve for dimension drawings, to find center lines and center points, or determine what a curve must be to fair in existing points, or lines, on a drawing. ACU-ARC adjustable curves are made of incredibly flexible, shape-holding butyrate plastic that can be finger-shaped to any curve for extremely accurate drawings and layout. Adjustable curves are perfect for quilters, designers, draftsmen, artists, and more. Alvin TRU-FLEX flexible curves are highly versatile drafting aids made of lead-core construction. TRU-FLEX flexible curves feature a raised inking edge, and graduations in both millimeters and inches.