How to Insert Ink Cartridge: </br>Step 1: Disassemble the Pen: Pull out the ink refill converter, then you can see a protrusion in the grip section, this part is what punctures the cartridge and carries ink to the tip. </br>Step 2: Insert the Opening into the Grip Section: Insert the cup-like rim end into the grip section </br>Step 3: Press Firmly: Push the cartridge in firmly until you feel the cartridge puncture. This may take more force than you expect. </br>Step 4: Leave the Pen Tip Down: Wait until ink saturates the feed. </br></br>Package Included: </br>6 fountain pens with different size nibs (0.7mm/1.1mm/1.5mm/1.9mm/2.5mm/2.9mm); </br>20 pcs ink cartridges (4 x Black, 2 x Red, 2 x Deep Blue, 2 x Orange, 1 x Yellow, 1 x Blue, 1 x Cyan 1 x Green 1 x Wine Red, 1 x Brown, 1 x Purple, 1 x Pink, 1 x Transparent, 1 x Fade ). </br>Ink Cartridge Size: Length - 50mm, Bore diameter - 3.4mm. </br></br>Customer Service: If you have any problems, just contact us, whether you want to replace your order or want your money back, we won't let you down. </br></br>This calligraphy set will help you develop your calligraphy skills, you can write a wide range of lettering styles with different pen’s nib. It’s a perfect gift for calligraphy beginners, it will help you enter into the wonderful world of calligraphy and creative lettering. </br></br>Warm Tips: </br>1. Keep the nib at an angle, between 30° and 45° to the horizonal line of writing. This angle must be constant to achieve the beautiful thick and thin style of letter. </br>2. Do not allow the ink to dry in the nib as this will stop the flow of ink. Carry and store your pen upright to prevent leakage. </br></br>Note: The trace of the combination of the nib and pen body is caused by glue bonding, not the ink residue.