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The Pentel 100w is a classic paint marker that's been around for over 20 years. It's pocket-sized so it doesn't take up much room and it's easily concealable. The 100w has a pump valve to control the flow of paint to the nib, which is a large 4mm fiber tip that stays juicy and doesn't streak. You can fray the nib to make it write even thicker lines if you want and it's metal body is damn-near indestructable. Another classic marker for your stash.