This is the "uni Propus Window" highlighter from Mitsubishi Pencil. Here's some information about this product: Features: The pen tip has a window, allowing you to see the text while highlighting, so you can mark cleanly without going over the lines. Pen Tip: It's a twin-tip with a broad chisel tip and a fine bullet tip, serving two functions in one pen. Ink: It uses special pigment ink, which provides vivid color and is water-resistant and light-resistant once dry. Uses: It's also compatible with OA paper and is less likely to discolor on fax paper, preventing the fading of text printed on non-carbon paper.