Northspore's Autoclavable Disc Filters for 'Regular Mouth' Mason Jar Lids are essential for those looking to preserve fresh food or liquids. The filters are designed to allow air to flow while keeping out dust, debris, and contaminants. They are made of durable, food-grade polypropylene, and are autoclavable up to 250°F/121°C. Perfect for long-term storage, these filters will keep your food and liquids safe, fresh