A disappointing speedometer. I took it out of the box and the reading window fell out. I pointed to a roll of tape I had on my bench and he said it was spinning at 7100 rpm. I pointed out other non-spinning things and was given a wide range of rpm. I pointed it at my CNC machine spindle which already has a piece of reflective tape on it and I couldn't get a consistent RPM reading. The laser target beam is only about 1/3. It looks like a crescent. I send it back and receive "AGPtekยฎ Professional Digital Laser Phototachometer, RPM Non-Contact Tachometer". It appears to have been made by another company. Hopefully it's a much better device. I understand these are budget speedometers, but they shouldn't fall apart when you flip them over to put in batteries.