The Starrett 98-6 precision machinists’ level is six inches long and has a graduation (also called sensitivity) of 0.42 mm/m, or 80-90 seconds. The level has two vials to provide accurate results. The main vial is ground and graduated with five lines and adjustable to a positive setting. A second cross-test vial allows measurements from two directions at once. An involute groove runs the entire length of the level base, and provides a reliable seat for round work, such as leveling pipes or shafting. The base is made of machined cast iron for increased durability, and the glass vial is housed in a brass tube with a friction-fit closing, to prevent breakage. The level is warrantied for one year. Specifications Dimensions 3 x 6 x 1-1/2 inches (H x W x D) Graduation 0.42 mm/m; 80-90 seconds Number of vials 2, level Vial material ground glass H is height, the vertical distance from the lowest to highest point; W is width, the horizontal distance from left to right; D is depth, the horizontal distance from front to back. Levels are instruments that are used to determine the true horizontal or vertical plane of a surface. The most common type of level is the spirit level, or bubble level. Spirit levels have a liquid-filled, bowed tube (also called a vial) with a bubble that moves when slight adjustments are made to the level. When the bubble settles between marked points on the vial, it indicates that a surface is horizontally or vertically straight. Levels can have one or more vials to determine the horizontal plane, the vertical plane, or various points between, such as a 45-degree angle, simultaneously. Some levels include a laser line indicator that projects a horizontal or vertical beam on a surface. Bullseye levels, or surface levels, are circular, flat-bottomed spirit levels that determine whether a surface plane is level. Machinists’ levels are made of metal and have surfaces designed specifically for rugged use in a machine shop or tool room. Levels can range from highly-complex and accurate machines, such as those used in the surveying and construction industry, to precision instruments used in carpentry and other building trades, to simple, pocket-sized devices for do-it-yourself projects. The L.S. Starrett Company manufactures precision measuring tools, metrology and testing equipment, and saw blade products. The company was founded in 1880 and is headquartered in Athol, MA.