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