If you have a chamber-type machine: Buy a chamber-type bag (mesh-less design). The open end of the vacuum bag must be the same size or shorter than the seal bar on your machine, and the bag must also fit inside your machine’s chamber.
If you have an external-type machine: You must buy an external-type, or "out of chamber" bag (mesh design). The open end of the vacuum bag must be the same size or shorter than the seal bar on your machine.
All of our
vacuum machine bags list how large the open end is, and whether you can use them with external or chamber machines, in the content.