These heavy duty 2 L 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. -A wide range of optional caps are available for these bottles -Polypropylene colored caps in a choice of orange green purple red and light gray for ease of sorting and identification. -Vented membrane cap with 0.22 mum PTfE hydrophobic membrane. -Red PBT (polybutylene terephthalate) solid caps and ETfE pouring rings for dry heat sterilization (180C). -PBT caps with silicone septa for syringe sampling or introduction of reagents.