These wide mouth PYREX® 500mL Erlenmeyer flasks have a large, 29mm neck opening which makes it easy to use larger volume serological pipets. Ideal product for use as a shaker flask or for media prep and storage needs. They also have a single size linerless, one-piece autoclavable orange polypropylene plug seal caps with GL45 threads and drip-free pouring rings. -A wide range of optional caps are available for these bottles including: -Polypropylene colored caps for ease of sorting and identification. -Vented membrane cap with 0.22µm PTFE hydrophobic membrane. -PBT (polybutylene terephthalate) solid caps and ETFE pouring rings for dry heat sterilization (180°C). -PBT caps with silicone septa for syringe sampling or introduction of reagents.