The spring converter works with fountain pen takes 3.4mm converter such as Hongdian fountain pen by removing syringe needle. Great for filling or flushing fountain pen ink cartridges, converter and bottled ink. Non-sterile, for industrial use only! Easy Assembling: This syringe filler comes with 3 parts ( converter, white connector and needle), Just attach the converter and needle with the connector at the correct end. You can do it easily if you wrap a cloth around it and add some grease on the connector. For the first time of assembling, you may need to push it a little harder. The spring converter works with Hongdian fountain pen when removing syringe needle. They are perfect for filling or flushing fountain pen. It is recommend to clean fountain pen at least one time per month to maintain your pen in good condition, these fountain pen auxiliary absorber will surely do the job. Easy to fill, just dip the tip into bottled ink, press the spring stick down, release the stick to draw ink up into converter. Dimension: Size: full length 13cm Color: red and black Package includes: 5pcs* inking aids