Drill Bit 1/2" x 18" Auger, Moly Coated. A number of Auger bit sizes are available. Generally the bit size should be 1/16” smaller than the plug that will be used. 13/16” and 7/8” bits are often used when performing fumigant treatments while 9/16” is used when installing borate rods. Please contact Poles, Inc. with specific questions about bit and plug size. Moly Coated bits offer improved performance and life cycle.