This large jar sealer cap is used with a wide mouth mason jar and lid. Place a canning lid with the red rubber seal on a canning jar. Place the cap over the lid and jar, attach hose to lid and then to machine. Operate the vacuum sealer to eliminate the air, unplug jar cap and lift off. The canning lid should be attached by vacuum to the canning jar. Repeat process on as many canning jars as needed. This process is used to store dry products such as dry fruit, nuts, flour, rice and many other dry pantry products. It is also used for resealing items such as canned fruit, and left-over meals placing them in a refrigerator for storage.