The product measures angles from 0 to 180 quite well. It comes with a second battery which is good as the battery in the device was dead. I bet that's a common story and that's why they include a second battery. My advice: send the angle viewfinder without a built-in battery. The set includes a carpenter's pencil and sharpener, a nice touch. My read/usage scores are low because left-handers are a bit uncomfortable to use. Your design can use both "left-hand" mode and "compliment" mode (where the display shows 90D minus the current value). I need to measure the "drop angles" relative to the vertical frame. Indicates that there is a 68D reading when searching for a 22D tilt angle.