Schmidt Black Medium with Metal Tube Rollerball Refill-Medium. This convenience is owed to an easy and smooth gliding over the paper. Pen manufacturers all over the world rely on liquid ink refills from SCHMIDT Technology. They are equipped with an end plug in their individual writing color and a protection cap in the color of the writing system. Schmidt Safety Refills avoid drying up by means of a sophisticated ventilation system and are designed for use in writing instruments without perfect sealing caps.