This portable pen filler allows you to carry fountain pen ink on the go, while also providing an easy way to refill your pen. It has a section that locks the pen in place for leak-proof filling, and a top to keep it closed when not in use. The max ink capacity is 10ml. Instructions are included. The Pineider Pen Filler will accept pens with grips that are between 9.5mm and 13.5mm