Acu-Arc adjustable spline curves are made of incredibly flexible, shape-holding butyrate plastic that can be finger-shaped to any curve for extremely accurate drawings and layout. One edge is flat-to-surface for pencil, and the other side has a bead for ruling pen. Adjustable flexible curves are perfect for quilters, designers, draftsmen, artists, and more. Still manufactured by hand, Acu-Arc rulers and curves have been used by architects, engineers, chiropractors, designers, draftsmen, artists, woodworkers, metalworkers, surveyors, carpet installers, and law enforcement for over 50 years. Acu-Arc adjustable curves are made in the USA.