Launch Rev Limiter Switch Box MSD7551Launch Rev Limiter Switch Box MSD7551 D7551 Instantly changes the launch RPM setting of the Programmable Controls Two control dials, one for 1,000 RPM and another for 100 RPM Adjustable from 3,000 12,500 RPM in 100 RPM increments Can only be used with programmable MSD Ignition Controls and Accessories This handy controller lets you change the launch rpm setting instantly for last second changes in track conditions. They plug into the RS232 computer