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Staedtler Mars Carbon Lead$8.64
These 2mm leads are consistently smooth to use as well as being robust, they seem to go on forever. Sold in packs of 12 of the same hardness. The leads can be used on paper and vellum - an indispensable tool for precise drafting, drawing, sketching, and writing.
The superior quality and strength of the specially bonded lead prevents breakage during use and sharpening!