Jacques Herbin's Vert Cactus is a mesmerizing green-brown (darker than olive) fountain pen ink that hits a balanced, earthy perfection. It reads as either a brownish dark-green or a greenish brown, just like you'd expect from something named "Cactus Green." Like all of Herbin's regular fountain pen inks, it is pH-neutral and therefore safe in all kinds of vintage fountain pens, including latex sac fillers (i.e. most vintage lever-filling pens) and celluloid-body pens. About Herbin Fountain Pen Inks: "The Jewel of Inks". Jacques Herbin inks are the oldest in the world. Made in Paris as they were in 1798, these fountain pen inks are non-toxic, lightfast, fast-drying, water-based and contain all-natural dyes.Each 30ml bottle comes boxed and is elegantly labeled with an integrated pen rest.Made in Paris, France.