On The Run OTR.070-R Hard To Buff - Round, complete with 10mm round pump action nib for wide lines. Filled with classic Hard To Buff ink, this is one of the best and strongest alcohol based inks available. It's an incredibly hard to remove deep black ink that is glossy and highly opaque. This ink will mark most surfaces and, as the name suggests is highly permanent. A multi purpose marker for broad lines and filling in larger areas.