Relocating your Air Filter is one of the most important steps when installing your HornBlasters horn kit. If you are mounting your compressor outside the vehicle, chances are it's going to get wet at some point in its lifetime. No problem, right? Only if your air filter has been relocated properly. If the air filter is mounted right onto the compressor, it can get wet and ultimately allow the compressor to suck in water along with air. This can/will lead to issues with the compressor and eventually failure.