The DIY kit comes with just about everything you need. Horns, compressor, wiring and all mounting hardware. You may need other supplies. You can use this kit for almost any impact driver and some drivers. (Will not work on Milwaukee M12 or Makita) 

PDF instructions included 

The DIY kit does work with Cars/ATV/Ect. 

-Metal horns

-Build time approximately 1 hour 

-No returns for this kit