Description The Pineider Pen Filler allows you to safely carry your favorite fountain pen ink with you, while providing an easy and clean way to refill your pen! Win, Win! The pen filler section locks the pen in place while filling your pen and the clear reservoir shows you your ink level. The maximum ink capacity is 10ml.The Pineider Pen Filler accommodates most filling mechanisms and most pens, except very thin or very thick pens. There are 2 handy holes on the side of the outer box so you can determine whether or not your pen will fit.To use, just insert your pen nib-first into the pen filler, turn the top to lock it into place, turn the entire thing upside down, and fill your pen! Instructions are also included, just in case!