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