Master Mechanic, #50, 2", BLACK oxide, wire gauge Number drill bit, jobber length, straight shank, 135 split point eliminates walking & provides quick starting, surface treated with BLACK oxide finish for abrasion resistance & improved chip flow, designed for precision hole sizing such as tapping threaded holes, wire gauge diameters fall between fractional sizes for most precise hole sizes, taps through sizes 1/4-28 require the use of wire gauge bits, Carded.