Abstract: An insert nestingly receivable within a centrifuge cup to support a pair of fluid containing bags therein is formed from a pair of concave shapes having an upper end and a lower end and which are centrally adhered together in back-to-back relationship. The shapes together with an interior surface of the centrifuge cup together form a pair of elliptically shaped chambers for supporting a pair of the bags within the cup. A pair of pins extend through the concave shapes and extend outwardly therefrom. The bags each are provided with a pair of spaced-apart holes to receive the pins, thereby supporting the bags within the elliptically shaped chambers. Preferably a block is fitted between the adhered together surfaces of the shapes at each lateral edge at the lower ends thereof. These blocks preferably extend laterally outwardly beyond the lateral extremities of the shapes, and the edges of the concave shapes and the blocks are rounded to thereby be nestingly receivable in the interior of the cup.