Hi, I have the Viair model # 25030-350C Which I use to run my air horns in my Jeep. This Compressor is 100% duty...12 Volts...17 Amp...1/4 H.P...I hooked up a one gallon tank to it. Which is more than enough and I'm glad because I'm strapped for space in my wrangler. This particular Compressor is not portable and most Viair's that I have seen are not unless you make your own hook up to the battery. I have had this unit for many years and it has been flawless.
One peice of advice is if you're going to buy a compressor of this type buy one that is 100% duty like I have.
If you look at the model # 32530/325C is 33% duty which means that it will run for 15 minutes but then it needs 30 minutes off to recover. Probably not a big deal but I wasn't willing to take that chance.
Most Viair compressors are rebuildable and are very easy to rebuild. I have had some experience with them on jeeps, lowriders,etc. David is correct look for a 100% duty compressor. You d be suprised at how powerful and quick this little compressors are.