Schmidt 5888 Fine Rollerball Refill - Black Ink Medium Tip - Black Ink - Standard Size Metal Body Ceramic Tip Roller Ball refill by Schmidt. Fits 98% of all Rollerball pens that accepts a standard size refill. Refill Reads: Private Reserve Ink 5888 M. Length 4 5/16 (11cm), Diameter - .245" (0.62cm) Non-dry refill.