Each of {HEAD ~ the components}, including {TAIL ~ the mirrors}, anode, and cathode, must be sealed to the block to form a gas tight seal 
Each of { HEAD ~ the components } , including { TAIL ~ the mirrors } , anode , and cathode , must be sealed to the block to form a gas tight seal
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH