Metronic Black Pen Ink Cartridge Refills Set, Set of 30 Refill Ink Cartridges,3.4 mm Bore Diameter for Calligraphy Pen and Fine Writing

[DIMENSION] Length Appr 52mm; Cartridge Diameter Appr 6mm; bore diameter 3.4mm.

[SMOOTH] With no break in ink flow, smooth; taking only a few seconds to dry and enjoying the best writing experience

[SAFE AND NON-TOXIC] The ink is made of safety dyes, neutral pH value, harmless and non-toxic
[PAY ATTENTION] Please confirm that the product diameter is consistent with the diameter of the interface on your pen before purchase

[AFTER-SALES SERVICE] We provide you with satisfactory service. Please feel free to contact us if you have any questions