Product Appearance: This product is made of a special mirror-finished acrylic material, providing crystal-clear transparency and a light transmittance of over 92%. Product Features: This product uses virgin materials and imported oil. Bubbles form in less than 1 second after impact. After storage at -20C or 65C for 12 hours and then returning to normal temperature, the bubbles return to their original size. Accuracy: Accuracy is also called sensitivity or angular value. For circular vials, accuracy is the angle of inclination of the vial when the bubble moves 2 mm in any radial direction from the center of the boundary line. For long vials, the accuracy is the angle of inclination of the vial when the bubble moves 2 mm along its axis. Metal vials: Metal vials are manufactured by cold machining an R-precision glass plate and an aluminum alloy shell. They are aesthetically pleasing, durable, and easy to install, with an accuracy of up to 2 mm. They are used in laboratory equipment, high-sensitivity balances, and other applications. Main applications: Level adjustment of woodworking tools, factory machinery, specialty instruments, pan/tilt systems, medical equipment, laboratory equipment, desks, computer cases and monitors, office machines, cameras, tripods, fixtures, photo frames, murals, calendars, toys, and other applications requiring high measurement accuracy. This makes it easier to level frequently used objects and achieve more accurate angles. Note: This is a simple teaching angle gauge. The needle may detach slightly from the central iron core during transportation, which may cause inaccuracy. To correct this problem, open the cover and gently press the needle to adjust it. (Be careful not to press the center of the needle, as the iron core may injure your finger.)