can be used to remove the formed collector piece 14 from the central core 58 by sharp downward pressure the pin 53 is centered by a spacer plate or collar 62 which may be integral with the block 52 or separate the crown 18 can be formed similarly from a straight pull mold having a cavity and central core slightly different than those of fig7 but which can easily be determined by one skilled in the art the retaining portion or crown 18 is then slid over the reduced diameter portion 22 of the collector portion 14 and locked into place by frictional engagement of the nubs 33 the retainer portion forms part of the annular groove for the o ring 40 and simultaneously holds the filter media 24 in place in use a liquid sample to be filtered is placed in the bottom of the reduced diameter portion 20 of the outer container 12 the plunger is inserted filter end first into the open end of the outer container 12 and the o ring 40 sealingly engages the inner wall to form an air tight seal between the outer container 12 and the plunger 14 as the plunger is depressed further into the outer container 12 air is forced through the filter media 24 and escapes through the loosely fitting cap 16 once the plunger reaches the surface of the sample fluid to be filtered a fixed quantity.