The Opus 88 Mini Pocket Pen is a pocket-sized eyedropper-filled pen with a piston operated shut-off valve. It comes with an eyedropper and is packaged in attractive Opus 88 boxing. An ebonite piston and rubber gasket seals the feed off from the barrel when fully tightened. This keeps the pen from leaking which is a common drawback of eyedropper-filled pens. To open ink flow to the nib simply loosen the rod inside the body by twisting the knob at the end of the barrel counterclockwise. For longer writing sessions or when flex writing it is important to keep the valve open. Features: Eyedropper-filled (eyedropper included) #5 JoWo nib units Screw on cap Unique ink shut off valve to prevent leaking. Dimensions: Length capped: 12cm (4.7") Length uncapped: 11cm (4.3") Length posted: 14cm (5.5") Diameter at grip section: 11mm (0.45") Diameter of body: 1.5cm (0.6") Weight: 26g (1oz)