OLO Markers are premium alcohol-based markers that feature OLO's patented cartridge free-flow ink system which maintains consistent, controlled ink flow throughout the life of the ink cartridge. Each OLO half marker contains 2ml of ink. OLO's unique design features let artists custom-build marker and marker sets. For example, the OLO Connector ring combines various OLO marker ink colors, nibs and more. Experience a new way to color with OLO accessories such as the Brush Handle. OLO brush markers provide a smooth, fluid feel while maintaining balance and control. OLO chisel markers are designed to provide optimal control for thin strokes. OLO brush markers are color-coded black and OLO chisel markers are color-coded gray for quick nib identification. Utilize an OLO Connector Ring to create unique double-ended markers that feature your choice of colors and nibs. All OLO nibs work with all marker bodies.