Spirit level vials, as mentioned, are small glass containers used in various industries for their precision leveling capabilities. The primary function of a spirit level vial is to provide a visual indicator of whether a surface is level or plumb. The design of the vial is simple yet effective, with a bubble floating in a liquid-filled chamber. When the vial is perfectly horizontal, the bubble floats to the center, indicating that the surface is level.

The key components of a spirit level vial include:

1. Glass Vial: This is the transparent container that holds the leveling liquid and the bubble. The glass is typically thick and durable to withstand the rigors of construction sites and other demanding environments.

2. Liquid: The liquid in the vial, often alcohol or water, serves to provide a medium for the bubble to float in. It is chosen for its density and clarity, ensuring that the bubble's position is easily visible and distinguishable.

3. Bubble: A small, air-filled cavity that moves within the liquid. When the vial is tilted, the bubble will move away from the center, indicating a tilt in the opposite direction. The size and consistency of the bubble are calibrated to provide accurate readings.

4. Scale: Most spirit level vials have a scale etched or printed on the side of the vial. This scale allows for the measurement of the degree of tilt, which can be important for precise alignments and measurements.