Bottles have permanent white enamel graduations and marking spots. Caution: do not tighten caps immediately after autoclaving. Each bottle includes a Linerless, one-piece autoclavable polypropylene plug seal cap. Replacement caps are not available for the 25-ml size. A pouring ring is not included with the 25-ml size. Heavy-duty borosilicate glass-perfect for storage, mixing, and sampling