Mast cartridges 100% E.O Gas Sterilized and individually packaged. One piece needle allows for maximum stability and control. Indentation at tip enhances ink flow and saturation. Membrane mechanism prevents ink spitback. Needles made of 316 medical grade stainless steel. Compatible with all popular pen machine and cartridges grips. High toughness silicone rebound maintains its original flexibility and strength with long time work. Smooth edges eliminate additional trauma. Precision assembly. Quality ensured with meticulous 30-point inspection, including pin alignment and solder distribution. Membrane mechanism prevents ink spitback. Low profile housing & better ink flow & shaped on the inside.