These heavy duty 500 mL 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 GL45 threaded cap with a drip-free pouring ring. New glass bead indicates full capacity line. 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. Vented membrane cap with 0.22 µm PTFE hydrophobic membrane.