Flange metal bubble vials refers to a type of spirit level vial that has a metal frame or casing with a flange, which is a projecting flat rim or collar used for attachment. This design allows for easier mounting or integration into machinery, equipment, or other applications. The metal casing, often combined with the flange, ensures that the vial is securely held in place and offers robust protection in various working conditions. When considering a flange metal bubble vial, factors such as the type of metal, the dimensions of the flange, the level of precision required, and the specific application or use-case scenario should be taken into account.