A cartridge for insertion into a meter comprises: a plurality of cartridge brackets disposed on an inner wall of the cartridge a spindle mounted so as to be rotatable within the cartridge and movable longitudinally in first and second directions within the cartridge and a plurality of testing members each arranged to be supported temporarily by at least one of the plurality of cartridge brackets, each of the testing members including a hole through which the spindle is located, the spindle having a plurality of spindle brackets disposed on an outer surface thereof, each spindle bracket being movable between first and second positions wherein in the first position the spindle bracket’s distal end is at a first distance radially from the longitudinal axis of the spindle and wherein in the second position the spindle bracket’s distal end is at a greater distance radially from the longitudinal axis of the spindle, and wherein when a given one of the spindle brackets is in the second position its distal end is located against a surface of one of the testing members so as to prevent movement of the testing member in the second longitudinal direction relative to the spindle. When the spindle advances in the second longitudinal direction relative to the cartridge, the spindle brackets are configured to move from the second to the first position so as to allow the spindle brackets to move past the testing members in the second longitudinal direction relative to the testing members, the spindle brackets being configured to return to the second position after moving past the testing members such that each spindle bracket is located against a surface of a different one of the testing members to the testing member against which it was originally located and such that the spindle brackets communicate force from the spindle to the testing members in the first longitudinal direction to move the testing members in the first longitudinal direction as the spindle is moved in the first
