The space provided between {HEAD ~ brush members} 4 a and 4 b allows {TAIL ~ a mounting strip} to be included in the housing 
The space provided between { HEAD ~ brush members } 4 a and 4 b allows { TAIL ~ a mounting strip } to be included in the housing
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH