Pentel X100W Permanent Marker Bullet Tip 3.3mm Line White (Pack 12)Over 30 years old, X100W is the biggest seller of its type and used in industry to mark non absorbent surfaces such as metal, glass, plastic and rubber. X100W White Marker has a thick bullet tip and gives a line width of approx 3. 3mm. Because of the china clay pigment it has a valve to control the flow of ink which passes down and around the tip, rather than through it.