... M42 Zirconium Coating, Black, Coffee Color HSS Double Ended Twist Drill BitsProduct Description:HSS Twist Drill Bits ... , Double EndedFully Ground4341,9341,M2,M35,M42 3.0mm ... immediately.* twice as many holes as a single end drill bit.* used primarily in small machine shops ... , sheet brass, sheet aluminum and plastic sheets. Double end drill bit