Jackson Safety 14783 Curv-O-Mark Jumbo Contour Markers, 40" RadiusModels available jumbo size for scribing circles up to 8" diameterSturdy friction joints maintain rigidity and accuracy, and are made from lightweight, rustproof aluminum for long wearSoapstone crayon is included. The scribe holder will accept round, square or flat soap stone crayon, pencil or steel point scribeFolding type design - three smallest models will fit conveniently into a shirt pocket