Thus, there can be an acceptable degree of {TAIL ~ lapse} in the rotational relationship between the valve disc and {HEAD ~ the stem} 
Thus , there can be an acceptable degree of { TAIL ~ lapse } in the rotational relationship between the valve disc and { HEAD ~ the stem }
OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD