Uni-ball Signo DX UM-151 Gel Ink Pen - 0.38 mm - Black (Set of 2) Users can enjoy clean and even flowing lines, and the strong tips can withstand all the heavy handed writing you can offer. Like all our other pens, the Uni Signo DX is highly sought after by artists and writers alike, but difficult to find in the US. Includes 2 pieces of 0.38 Gel Ink Pen.