This machine is yet another good example of high quality Hitachi engineering.  This compressor has outlasted several other brands.  The machine has run two finishing guns continuously for almost a year and  hasn't needed anything more than an oil change The regulator is  predictable, and adjusts as easily as other brands.  I firmly believe that  Hitachi gets 4.1 CFM out of 14.5 amps.  We simply do not run out of air no  matter how fast we are working with the Senco SFN40's.  Down time has  been zilch.  One thing we did add was a water/oil separator and filter to  protect our work and our guns.  I suppose Hitachi (and most other brands)  leaves these off so that they will have a competitive price.  But it does  not make economical sense for YOU to leave them off.