A reaction vessel suitable for multiple assay utilization within an automated, continuous and random access analytical system which allows for kitting of sample and reagents and physical transfer of the kitted reaction vessel to a process carousel is disclosed. The reaction vessel comprises multiple wells of various volume capacities, the multiple wells having openings on the same plane and depths extending from said plane. The reaction vessel has at least one cuvette, which extends substantially below the multiple wells and has an opening on the same plane as the multiple wells. The reaction vessel further comprises a transfer projection on a well bottom portion of the well on a first end portion of the reaction vessel, the cuvette projecting downward from a second end portion of the reaction vessel.