The Extech 461891 contact tachometer measures the contact surface speeds (10 to 9,999 rpm) of rotating objects. The memory button stores the last measured value and calls up the MIN/MAX measured value display. The wheels are suitable for linear surface speed (0.05 to 1999.9 meters/minute) or rotational speed measurements. The scope of delivery includes a cone tip, flat tip and a spare wheel for linear surface speed measurement, four AA batteries, a carrying case and a user manual.