-Construction marker. Functional pressure mechanism for automatic lead advance, simple one-hand operation with clip, integrated sharpener with guide - allows quick sharpening directly on the trousers, leads can be easily refilled from the front and back, for all surfaces (wood, metal, glass, ceramic, etc.), included special graphite lead can be wiped off smooth surfaces with a damp cloth, separately available colored replacement leads for use on light and dark surfaces. Replacement lead for (-item no. 21 3150) - 12 pack replacement leads (3x red, 3x yellow, 6x graphite)