Noodler's Baystate Blue ink in a 3 oz bottle. Baystate Blue is a forgery-resistant, waterproof, and vibrant blue ink.
Noodler's Ink bottles come filled to the brim, so be careful when opening!
Baystate's vibrant blue color comes with a caveat: Its unique pH levels can stain parts of your pen and/or anything it comes in contact with (porous surfaces like sinks). Feed sections, converters, demonstrator pens, and plastic pen parts are susceptible to permanent staining. Although the internet has much to say on Baystate Blue, feel free to experiment with it (including diluting it) - but exercise caution and practice good pen hygiene when using this ink.