The higher protruded walls 4011, 4021, 4031 thereof are circumscribed by a lower stop wall 404 extending upwards at {TAIL ~ the outside} thereof to form a channel groove 405 therein for {HEAD ~ the sealing ring} 43 of the same shape to be adapted in sleeve engagement therein 
The higher protruded walls 4011 , 4021 , 4031 thereof are circumscribed by a lower stop wall 404 extending upwards at { TAIL ~ the outside } thereof to form a channel groove 405 therein for { HEAD ~ the sealing ring } 43 of the same shape to be adapted in sleeve engagement therein
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH