A microwell cluster was manufactured with silicone rubber for incubating thin sections for postembedding electron microscopic immunocytochemistry. The small size of the wells requires only minute amounts (as little as 5μl) of antisera and other valuable immunoreagents. The capillary action of the wells holds the incubation media and grids in place, even if the cluster is turned upside down, thus facilitating safe transport and storage of the sections to be stained. This silicone rubber microwell cluster can also be used as a die to imprint wells in Parafilm sheets to be used for the same purpose.