30 is made of a compressible elastomeric material such as polyisoprene rubber plunger rod 50 is made essentially of the same material as the barrel referring to fig1 3 4 and 6 plunger 30 is slideably received in barrel 20 and is moved axially in the barrel by a manual force exerted on plunger rod 50 which is engageable with plunger 30 plunger 30 in its relaxed state resembles an inverted cup having a distal convex outside face 32 a proximal inside face 34 outside wall 36 contiguous with distal convex outside face 32 inside wall 38 contiguous with inside face 34 and bottom rim 39 which defines the circular opening in the cup shaped plunger 30 distal convex face 32 of plunger 30 is to interface with a fluid contained in barrel 20 outside wall 36 of plunger 30 comprises distal ring 40 proximal ring 41 and center ring 42 which are elastically deformable and extend radially outwardly from outside wall 36 and have when taken together with plunger 30 a minimal diameter slightly in excess of the largest diameter of the working section of barrel 20 the rings form a sealing but slideable engagement with inside wall 21 of barrel 20 inside.