a pen tip structure comprises an elongated stem which defines a cylindrical outer surface and a flat end surface , the flat end surface including one or more grooves which extend from the cylindrical outer surface radially inwardly towards a center point thereof , a tube positioned around the elongated stem , the tube including inwardly - extending protrusions that form at least one longitudinal ink flow channel along the cylindrical outer surface of the elongated stem , and an end portion which is located beyond the flat end surface of the elongated stem , the end portion providing a mouth , and a rotatable member positioned between the noted mouth and the flat end surface of the elongated stem , the rotatable member having a surface portion which extends beyond the mouth for conveying ink to a receiving surface and an opposite surface portion for receiving ink supplied thereto by capillary action . the longitudinal ink flow channel supply ink to the groove in the flat end surface of the elongated stem , the ink being reliably supplied to the surface of the rotatable member under all writing conditions by capillary action .