a main cylindrical member, extending in {TAIL ~ the axial direction} of said housing sections, for movably containing said {HEAD ~ housing sections}, 
a main cylindrical member , extending in { TAIL ~ the axial direction } of said housing sections , for movably containing said { HEAD ~ housing sections } ,
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH