The tachometer instrument comes with a replaceable array of contact adapters that can be used to measure rotational contact speed. The device is easy to read and understandable making it perfect for measuring fans speed, the speed of lathes, turbines, conveyor belts, belt motors and other elongated rotational systems. To make readings on your machine, prepare the surface with a reflective mark (comes with the package) then point the laser beam to the marked surface, the reading can now be displayed on the high resolution LED screen. The kit comes with an instructional manual, 4 x AAA Battery, reflective mark. The screen comes with a black light in case of dark areas. With an average of 4.4 customer star rating, the instrument is the best performing tachometer you can get at an affordable price.