The Sparco SL-C3 is a compact microprocessor –controlled rev-limiter/shift light. What makes the SL-C3 unique is that it has an internal relay that can be used to trigger a rev-limiter, water injection, nitrous injection, etc. The internal relay is controlled by the rev-limiter setting which can be set separate of the shift lights. The SL-C3 has a sequential 7 LED display that can be adjusted for brightness. The display has 3 different visualization modes: dot, bar, and bar with peak hold. The LED’s are programmable to flash in 100-300rpm increments. Installation of the shift light is straight forward. The unit only requires you to hook up 3 wires for the shift light to work (power, ground, and ignition signal). Additional wiring is required for the relay output. Sparco always recommends installation by a professional if you don’t feel comfortable with electrical wiring. You will be working on signal wires going to the computer that are vital for the engine to function properly.