Longacre Accutech SMI Tachometer - Black Face With PanelLongacre's stepper motor style tachometers use a small electric motor to drive the pointer for increased accuracy over more traditional air core instruments that are easily effected by the windings. This style of tach is so accurate that many professional teams are making the switch just look at any in car TV camera!) The easy to read 4 1 2" tachometer features a max RPM recall button, and a 2 stage LED warning light that also doubles as a 2 stage