P.W. Akkerman is a pen store in The Hague, Netherlands that was founded in 1910. To celebrate their 100th Anniversary in 2010, they released a line of inks with a very distinctive ink bottle.

The Out of the Blue ink bottle fills by tipping the bottle upside down so that ink flows from the large bottom section, into a small upper section. When you tip the bottle back up, a small marble rests in the neck of the bottle to create a reservoir, making it easy to fill the fountain pen. The P.W. Akkerman bottles contain 60mL of inks, while the names of each colour has been named after a different location in the Hague.