Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Useful?....NOT!

I purchased this product after reading some reviews which rated it higer than other similar ultrasonic measuring tools. In general, the reviews for ultrasonic measuring tools were negative but the Zircon was rated OK in several reviews. I have tested this unit for accuracy and repeatablility of meaurements from a few feet to 20 ft. or more (all indoors)and find it UTTERLY USELESS. Except for the case where you are measuring a distance to a flat, unobstructed, LARGE wall surface across a room with no obstructions OF ANY SORT (i.e. no furniture, light fixtures, curtains, pass-throughs, etc.) there is no repeatability. In repeated tests over the same distance, I found that displayed distances varied not by inches but by feet. It would be impossible to trust the measurements displayed by this unit. My advice would be to pay the extra money for a true lazer measurer. I have one on loan and it is astoundingly accurate, even in a cluttered indoor environment.