These heavy duty 25mL PYREX round bottles can be used for storage as well as mixing and sampling. They include a linerless, one-piece autoclavable orange polypropylene plug seal GL25 threaded cap. A pouring ring is not included on the 25mL size. Optional red PBT caps and red ETFE pouring rings are available for dry heat sterilization (180°C). Bottles have permanent white enamel graduations and marking spots. Caution: DO NOT tighten caps immediately after autoclaving as the vacuum resulting from cooling can cause breakage.