Screw on speed sender used when running a TH350/TH400 or powerglide and needing a speed input into a LS ECU. Comes with a mating connector ready to plug into a factory loom. Most common use is VT-VY LS1's running TH400 or powerglides. Note - will require tuning/calibration once fitted and also requires the speedo drive in the gearbox so unit can be fitted.. If running an older car with cable speedo you can select the Pass-Thru option which allows you to run the speed signal into the PCM while still allowing the speedo cable drive to the factory speedo.