Compressor Head Air Filter Replacement 3/8" MPT npt thread. Paper Cartridge Metal Body. Air filters are one of the most critical factors to in your compressor. It removes solid particles like dust and bacteria from the air, so that your compressor works with optimum performance. This replacement filter is a common filter used on many brands of compressors. It has metal body and comes with a disposable sponge filter. Comes with a disposable paper cartridge type filter element.