Pilot CON-40 Twist Piston Fountain Pen Converter

This converter is is known as a twist piston. Twisting the piston while immersing the nib section in an ink jar draws the ink in. It holds just under .5ml of ink.
 
This converter is compatible with nearly all Pilot pens, including the Metropolitan MR, Vanishing Point, Falcon, Plumix, Kakuno, Parallel, Prera, and others.