A separator tube for insertion into a collection tube comprises a tubular member having {HEAD ~ one end} closed by {TAIL ~ a plug} 
closed by
A separator tube for insertion into a collection tube comprises a tubular member having { HEAD ~ one end } closed by { TAIL ~ a plug }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL