comprising each of said sockets comprising a first end portion connected to the associated first pipe, a second end portion in which the plug body of the associated plug is detachably attached, and a rear cylindrical member having {HEAD ~ an internal hole} communicating with {TAIL ~ the associated first pipe}, 
communicating with
comprising each of said sockets comprising a first end portion connected to the associated first pipe , a second end portion in which the plug body of the associated plug is detachably attached , and a rear cylindrical member having { HEAD ~ an internal hole } communicating with { TAIL ~ the associated first pipe } ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH