Monroe's engineers have developed the best available universal twin-spool ribbons for calculators, the Monroe P65M. The Monroe P65M ribbon has been recognized as the highest-quality ink ribbon on the market for printing calculators because of its dark print and True Red color. Unlike most ribbons, Monroe has perfected the process of loading the highest amount of ink into the nylon ribbon. Additionally, instead of using generic red inks that produce an orange tint, Monroe has developed their True Red color. Users love the richness of the ink impression that both the black and red colors of our Monroe ink leave on their calculator paper. To optimize the print quality we suggest using Monroe's 20lb. calculator paper, this is a Monroe exclusive and it is the thickest calculator paper produced. This ribbon will fit nearly all Monroe printing calculator models as well as other printing calculator makes and models on the market.