Made of stainless steel and, it will not rust, deform, durable and easy to clean. Great for filling or flushing fountain pen ink cartridges, converter and bottled ink. You can do it easily if you wrap a cloth around it and add some grease on the connector. Easy to fill, just dip the tip into bottled ink, press the spring stick down, release the stick to draw ink into converter. Just attach the converter and needle with the connector at the correct end.