Thank you for your recent inquiry with The Home Depot. Cobalt bits are a special formulation of high speed steel with cobalt added in to withstand very high drilling temperatures. Cobalt bits are specifically designed for drilling very hard, abrasive materials. Cobalt bits are not designed for general purpose use. High Speed Steel bits are standard general purpose bits with a polished finish. We appreciate your business and look forward to serving you in the future. -The Home Depot-
Hello it is 6" overall length. Thank you.
I checked the package my bit came in and also the bit its self and the is not a RHC number or level code listed.
The only answer could be supply and demand. More want the six inch so it cost more.