uni-ball Products - uni-ball - Onyx Roller Ball Stick Dye-Based Pen, Micro, Dozen - Sold As 1 Dozen - Precision tungsten ball. - Excellent for carbons and multi-part forms. - Easy to hold matte black barrel. - Liquid ink. - Precision tungsten ball. Excellent for carbons and multi-part forms. Easy to hold matte black barrel. Liquid ink.