Precision Twist Drill Jobber Length Drill Bit: 5/16" (0.3125) Dia, 135 deg, HSS Oxide Finish, 4-1/2" OAL, Right Hand Cut, Regular Spiral Flute, Straight Shank, Series R10B-R15B-R18B MSC# 78502986 Mfr# 5998020 Ordered as Part #: 78502986 Big Book# 23