Pentel of America, Ltd 504H Hi-Polymer Lead, 0.7 mm, Medium, 4H, Black Sold as 12/TB. Super Hi-Polymer Lead Refills produce crisp lines of consistent darkness, smoothness and density in mechanical pencils. Each super-strong lead writes as far as an entire wooden pencil and produces a dark line. A 12-piece tube is equivalent to 12 wooden pencils.