Use this Uni-ball ZENTO gel ink refill in the pens listed under Compatible Products.
Its specially formulated ink reduces writing friction as well as feathering and bleed through.
Since the ink isn't getting washed out by the paper, dark inks look darker, and bright inks look brighter.
The ink is fast drying and bleed resistant too, so your notes will always be crisp and free of smudges.
Type: Refill
Nib Size: 0.38 mm, 0.5 mm
Diameter: 6.0 mm
Ink Composition: Water-Based
Size: 11.2 cm
Standard Refill Style: Euro Style
Tip Material: Metal
Tip Type: Conical
Water-Resistant: No
Weight: 3 grams
Brand: Uni
Manufacturer: Mitsubishi Pencil Co. Ltd., Higashidai Shinagawaku Tokyo