Rohrer & Klingner Blau Permanent (Blue) Ink

Rohrer & Klingner Blau Permanent is a beautiful muted dark blue color. This is one of my favorite "business-friendly blue" fountain pen inks, because it's so well behaved, even on cheaper, lower-quality (non-fountain-pen-friendly) paper.

Despite its name, this is NOT a permanent/pigment ink, but rather a dye-based ink (I wrongly believed that it was waterproof for a time, before realizing that my life was a lie). This ink is made in Germany.