2 Gel-Type Ball Point Refills (blue ink). German-Made. Medium line. Fits all Xezo ball point pens. Fits other brands selectively; interchangeable with standard Parker ballpoint refills. Approximate writing length per each refill is 1,300 meters/4,265ft/0.80 mi. Length: 98.06 mm (9.806 cm) / 3.86 in. Diameter: 5.8 mm (0.58 cm) / 0.228 in. Fits more than 99% of types of pens that accept standard Parker style Ball Point refills. Shelf life is approximately 1.5 years. Shelf life can vary depending on the temperature and moisture of storing. Avoid extreme heat or extreme cold.