Uni Pin Uni-Ball Black Calibrated Marker Pen Polyacetal tip. Plastic (PP) barrel. Uni Pin calibrated markers are ideal for professional drawing, artistic drawing and writing, offering a sharp and smooth stroke at the same time. Pigmented ink with high water resistance that once dry cannot be erased even if water is poured on the page, also has a high resistance to light and its color does not diminish even when exposed to direct light. Available in various thicknesses. Color: Black. Brand: Uni-Ball.