This is the only truly affordable genuine digital goniometer on the market. It allows rapid, precise and repeatable measurement of joint range of motion. It contains 2 poly fiber blades that are 10″ long and have graduations in millimeters and 1/16″ increments. From the “zero” setting it measures 360 degrees in both directions. Both blades have center lines to align one blade with stationary axis and the other with the moveable axis. Relative “zero” can be set at any point in an arc. It has a large LCD display that displays continuously as the blades are adjusted. Degrees are displayed in .05 degree increments (5 hundredths of a degree) and has an accuracy of +/- .5 degrees (half of a degree). It contains a “hold” function so you will never forget a measurement. It uses a 3V lithium ion battery that will last one year with normal use. Comes with one battery installed and one extra battery. Unit powers down after 5 minutes of nonuse.