Bottles have permanent white enamel graduations and marking spots. Caution: do not tighten caps immediately after autoclaving. Bottles larger than 2 L should not be used under vacuum pressure, as breakage may occur. Each bottle includes a Linerless, one-piece autoclavable polypropylene plug seal cap with drip-free pouring Rings. Optional red PBT caps and red ETFE pouring Rings are available for dry heat sterilization (180ºc), order separately. Heavy-duty borosilicate glass—perfect for storage, mixing, and sampling 10-l capacity.