This Uni Ball Posca Pen features an Ultra Fine 0.7mm Pin Tip loaded with highly-pigmented lightfast ink. The free-flowing lucid ink is a water-based formula that's quick-drying and waterproof and can write with ease on virtually any surface. Its ink is permanent on porous surfaces and removable on smooth surfaces such as glass, metal or plastic. Whilst its ink is dense and vibrant, it does not bleed through paper.