These heavy duty 50 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 GL32 threaded cap and a drip-free pouring ring. 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.