With the 461893, you can make non-contact RPM measurements (5 to 99,999 RPM) of rotating objects by pointing the integral light beam (6 in. target distance) at reflective tape placed on the object to be measured. The memory button holds last reading and recalls min/max readings display. Comes with 4 AA batteries, 23 in. (0.6 m) reflective tape, carrying case, and user manual.