A powerful inflator, with a great screw-on hose design, and a so-so gauge.What I like best is the screw-on hose.  No more trying to flip a clamp quickly enough to prevent losing air from the freshly-inflated tire (or deflating it further when you first attach the inflator)-- there's the briefest hiss of air when you screw the hose onto the valve.  This feature alone is to make me really like the BellAire 4000.Also, it fills the tires faster than my standby battery-poweredSlime COMP07 Inflator, and much faster than either of my old (since-retired) 12V inflators. I have not had any problems with it blowing out the 12V socket's fuse, although that is a risk with this kind of inflator.The unit is compact, not as loud as other inflators I've used. It comes with a nylon carry-bag (fitted to not add bulk) which will decrease the inevitable gunking-up of car accessories that live in the trunk, and has storage for both the hose and power cord (which also keeps them from being damaged as they ride around in your trunk).  The power cord seems long enough for most standard passenger vehicles. All of these are signs that the designers were actually thinking about how this inflator will be used and stored.The flashing hazard light is a nice touch also, in the unfortunate case of needing to do a roadside inflation. The onboard worklight has 3 small LEDs in a swivel head, which is handy, but would be more useful if brighter.The major flaw in the unit is, predictably, the pressure gauge, which is only vaguely accurate (analog) and has an outer dial to set the desired pressure.  The inflator is designed to stop when the pressure set on the gauge is reached, but since the gauge isn't accurate, I got results like setting the gauge to above 35, with 31 PSI in the tire, and having the unit refuse to fill until I set the dial to 40PSI.  This means you need a separate tire pressure gauge and may have to disconnect the hose a couple of times to check the actual pressure.  Effectively, the pressure setting becomes only a safety cut-off "ceiling".So what this inflator could really use is an onboard, accurate digital gauge.  Since I can buy a decent, accurate, handheld digital gauge for 10 bucks, it seems like integrating that function into an inflator should be easy.Other quibbles: The tight-fitting nylon bag is almost too small.  The cable storage compartment could be a little bigger. The carry-handle is a simple plastic ring that protrudes from the top of the inflator-- a proper padded handle (maybe a T-shaped one) could have fit in the same spot.  Without the handle, the unit is a bit awkward to carry one-handed (although it isn't heavy).The one big feature I would add to this unit would be an AC-power adapter, since when I use it in my enclosed garage, I have to open the garage door, start the car, back it out partway, and then use the unit.  An AC adapter would make it so I could just plug into the wall at home, but still be able to do emergency roadside work with the 12V adapterSo could this inflator be improved? Certainly, with a better handle, more accurate and digital gauge, a brighter LED, and support for AC power. But hands-down it's the best tire inflator I've used, so I still give it 5-stars.  Recommended.