The number of guide bars in {HEAD ~ each circular concentric series} increases from the radially inner series to {TAIL ~ the radially outer series} of guide bars 
The number of guide bars in { HEAD ~ each circular concentric series } increases from the radially inner series to { TAIL ~ the radially outer series } of guide bars
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH