{HEAD ~ The small grooves} 22, 23, 24 and 25 are close to {TAIL ~ rows} of V shaped grooves 26, 27 and 28 and a set of spiral grooves 29 similar to those shown in FIG 2 
are close to
{ HEAD ~ The small grooves } 22 , 23 , 24 and 25 are close to { TAIL ~ rows } of V shaped grooves 26 , 27 and 28 and a set of spiral grooves 29 similar to those shown in FIG 2
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH