The Brunson 194-TM Coincidence Level has a sensitivity of one arcsecond, and the beauty of using this split-bubble level is the ease which you can see that it is exactly level. By looking through the rotating turret, you can see both ends of the bubble when they are close to level, and when you adjust the level to the point where both ends align with each other- it is exactly level! This is the level used on most of Brunsons instruments such as the 545-190, 76-RH, 75-H and 771-H. This level is mounted to the top of these instruments and can be damaged by an inattentive operator. Here are replacements to keep you in business. To make sure this will fit, the mounting holes are located 5.225" apart.