Medline 19568 universal test tube rack medline 19568 the medline 19568 universal test tube rack is made from white autoclavable polypropylene and is specially designed to ensure that all the test tubes will be incubated at the same temperature an alpha numeric grid reference on the top tier of the rack allows easy sample recording and location the medline 19568 universal test tube rack is easily assembled and dismantled for cleaning and are stackable when unloaded medline universa