After my last tire went flat I finally decided to buy a portable air pump. When I went to change a tire, I found that my spare tire was also under-inflated. I did a little research by reading Revain reviews and settled on a RAD 12 volt portable electric air pump. I just tried it and was pleasantly surprised at how well it works and how well made it is. It is mostly metal and the components appear to be of very high quality. The cable is very long, so when connecting to the car, you can easily reach all four wheels. The device vibrates slightly when it's on, but if you just hold it or place it on a small square rug, it will stay in place. It inflates very quickly and I hope to update this review with the time it takes to inflate a tire. Another great thing about this pump is that it comes in a sturdy case that you can fit all the parts and the unit into yourself, saving space. I suggest buying an AC adapter so you can use it indoors.