Polypropylene rack has 96 wells to accommodate 0.5 ml micro centrifuge tubes on one side, or 96 wells for 1.5 to 2.0 ml micro centrifuge tubes on the other side. Arranged in standard 8 x 12 array. Handy lid snaps into place in the tabs on each end of rack. Grid lines are molded on the side of the rack that accommodates the smaller tubes making it easier to see the wells. Raised rings are molded on the opposite side of the rack making it easier to replace the 1.5 to 2.0 ml tubes from those wells. Rack measures 9.75 x 4.75 x 1.875".