A Bamboo Duo uses a high quality standard ball pen mini cartridge with a 0.7mm ball point size and black ink color. Replacement refills in black and other ink colors are generally available from stores that carry ballpoint refills.
Please make sure that the mechanical dimension of the refill purchased is as follows: 67.2 x 2.3 mm (length x refill diameter). To help you find appropriate refills quicker, we have compiled a list of refills from popular brands that are compatible with Bamboo Duo:
- Mitsubishi SE-7
- CROSS 8518-4
- LAMY M21
- Kaweco Soul 1.0
Please note that this list applies for all generations of Bamboo Duo, from the first generation up to the fourth.