Sailor fountain pen refill 0104

Product code
[Black 0.7mm]
：18-0104-220
[Red 0.7mm]
：18-0104-230
[Blue 0.7mm]
：18-0104-240
JAN code
[Black 0.7mm]
：49-01680-28004-0
[Red 0.7mm]
：49-01680-28005-7
[Blue 0.7mm]
：49-01680-28006-4
Specifications
Font width: Fine
Tip: stainless steel 0.7mm
Application: For oil-based ballpoint pens
Body size
φ2.5×90.5mm
Body weight
1.5g
package
celery pack
Size: 35 x 150mm (35 x 180mm when using header)
Weight: 3.5g

How to replace and refill the core