Adjustable - The vials are adjustable to a positive setting. It can be adjusted by turning the knurled knob on the side of the level, making it easy for quick leveling tasks. Durable Fine Finish - The base is made from cast iron and is precision-machined on the reference surface to increase durability. The vial is housed in a satin finished brass tube with a friction-fit closing cover to prevent breakage. Accurate and Precise - With the cross test vial, it is possible to simultaneously level in both directions. This prevents inaccuracies in the main vial reading caused by canting the level sidewise on round work. Ergonomic - The base of the levels features an involute groove between the bearing flats for accurate seating on round work. This groove has a special involute design, permitting better centering and greater capacity to handle larger rounds. The Standard for Excellence - Proudly made in the USA, Starrett combines over 140 years of American heritage and innovation with globally sourced materials to deliver exceptional quality tools and products.