An apparatus for presenting samples of liquid contained in like size sample containers for automated testing by a particle counting system, said like size sample containers being of the type each having a base, a continuous sidewall having an inner wall surface and an outer wall surface each extending upwardly from said base and terminating at a top end to define an upwardly facing open mouth, with an engagement portion of said outer wall surface being wider than said base, the apparatus comprising: a base member having an upwardly directed planar reference surface adjustably mounted on the base member by at least three gimbal mounts for adjustment of its horizontal level; a container positioning member having a horizontally extending main body portion with a plurality of substantially vertically disposed container-receiving sockets formed therein, with said container-receiving sockets each being open at a top end and a bottom end, with each said container-receiving socket being defined at said top end by a container-receiving rim portion; wherein said container-receiving sockets are positioned, shaped and dimensioned such that, when the apparatus is in an in-use sampling configuration, said like size sample containers are each positioned within a respective container-receiving socket with the bases of said sample containers projecting through the bottom ends of said container-receiving sockets to be supported in weight bearing relation by said reference surface, and such that, when the apparatus is in an in-use sampling configuration, a gap exists between the engagement portion of the outer wall surface of the like size sample containers and the container-receiving rim portion of the respective container-receiving socket; and wherein said container-receiving sockets are positioned, shaped and dimensioned such that, when said apparatus is removed from said in-use sampling configuration by removal of the container positioning member from positioning over the reference surface, each of the like size sample containers moves downwardly from its position in the in-use sampling configuration relative to the container positioning member to be supported by the engagement portion of said outer wall surface contacting the container-receiving rim portion of the respective container-receiving socket in weight bearing relation therewith. a base member having an upwardly directed planar reference surface adjustably mounted on the base member by at least three gimbal mounts for adjustment of its horizontal level; a container positioning member having a horizontally extending main body portion with a plurality of substantially vertically disposed container-receiving sockets formed therein, with said container-receiving sockets each being open at a top end and a bottom end, with each said container-receiving socket being defined at said top end by a container-receiving rim portion; wherein said container-receiving sockets are positioned, shaped and dimensioned such that, when the apparatus is in an in-use sampling configuration, said like size sample containers are each positioned within a respective container-receiving socket with the bases of said sample containers projecting through the bottom ends of said container-receiving sockets to be supported in weight bearing relation by said reference surface, and such that, when the apparatus is in an in-use sampling configuration, a gap exists between the engagement portion of the outer wall surface of the like size sample containers and the container-receiving rim portion of the respective container-receiving socket; and wherein said container-receiving sockets are positioned, shaped and dimensioned such that, when said apparatus is removed from said in-use sampling configuration by removal of the container positioning member from positioning over the reference surface, each of the like size sample containers moves downwardly from its position in the in-use sampling configuration relative to the container positioning member to be supported by the engagement portion of said outer wall surface contacting the container-receiving rim portion of the respective container-receiving socket in weight bearing relation therewith.