Staples Arc System Pink Notebook Expansion Discs 12-Pack 1.5 Diameter 1 1/2" New. Discbound discs are 1 1/2 inches diameter, 38.1mm. Increase the size of your discbound notebook to add extra pages and accessories. Holds 200 sheets of paper. Contains: 1 package of twelve 1 1/2" Pink discs. New, unused, some of the packs I have listed have come open at the back.