A rolling cutter unit for {HEAD ~ the rotary head} of {TAIL ~ an earth boring system} that functions to form a passage through earth formations, comprising: 
A rolling cutter unit for { HEAD ~ the rotary head } of { TAIL ~ an earth boring system } that functions to form a passage through earth formations , comprising :
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH