Fits standard wooden pencils. Centre hole holds pencil in perfectly centred position, and notches for offset marking allow scribing of off-centre lines, or lines near the edge of large panels. Offset notches account for the tip width of a sharpened pencil for an accurately scribed line. Integral magnet allows easy storage on ferrous metal surfaces. Offsets: 1.5mm, 3.1mm, 4.7mm, 6.3mm, 7.9mm, 9.5mm and 12.7mm (1/16", 1/8", 3/16", 1/4", 5/16", 3/8", 7/16" and 1/2") .