Each with its own specific application and fit, a variety of closures are available for use with flasks. Most common flask closures include screw caps and snap caps. Flask closures are typically manufactured from autoclavable plastics such as polyethylene or polypropylene. A wide range of flask closure types are available to accommodate a broad range of laboratory applications and flask varieties, including closures that are sterile or non-sterile, disposable or reusable, and vented or unvented. Vented flask closures commonly include a 0.2 µm filter membrane to prevent contamination of flask contents. For applications that require a tight seal, screw caps with plug seals are available.