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