As other reviewers have noted, the cigarette lighter plug supplied with this unit is, to put it charitably, fragile. It shattered the first time I attempted to pull it out of the socket. Fortunately, I had other compatible plugs handy that weren't needed for other devices, so I soldered the 12V leads from the compressor into a new plug. Now it works fine.
OK, it's noisy and slow, but for a cheap unit, it seems to pump effectively. With it, I can refill the spare tire on my Prius, which requires 50 psi. All small pumps take a while to fill a tire, but using this unit is a lot easier than delivering 100 strokes with a hand pump.