Delta Capless Mini 8126 - Blue Suitable for Delta Dolcevita, Montegrappa Micra and other Mini-Rollerball Pens One Year Cap-Off Time Nib Size: Medium (0.6 mm) Ruby Ball Length ? 3.00 inch (76.0mm), Diameter - .230 inch (0.58cm) Metal tube with tampon system, stainless steel tip with 0.6mm ruby ball.