The flange includes a first portion 12 of acetal material and {TAIL ~ a second portion} 14 of {HEAD ~ an acid resistant material} provided directly over at least certain regions of the first portion 12 
The flange includes a first portion 12 of acetal material and { TAIL ~ a second portion } 14 of { HEAD ~ an acid resistant material } provided directly over at least certain regions of the first portion 12
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH