If you can afford it, get one w/ over 10 cfm @ 90 psi. Of course that'll be a hard wired 220v compressor, and it'll cost $500+. I had to recently give up my 220 compressor and get a 110 just a few months ago. It's an oil head compressor like my old one and puts out around 7/9 cfm @ 90/40 psi. Its a Craftsman Professional and I paid around $350 for it. With this setup impacts and air ratchets are no problem. As was said before, it's the DA that'll kill it. That along with an air file, a cutoff tool (like the die grinder, but bigger) and sander/grinders. These tools usually need 9 cfm @ 90 psi and my compressor can run 'em, but I have to stop every once in a while so the compressor can rest. As for your question though /forums/images/graemlins/tongue.gif.... IIRC, I think most good guns, siphon and gravity feed, need from 9-12 cfm @ 40psi, and its recomended that you get a compressor a couple cfm higher than the range you intend to use it. Of course if we all followed that advice we'd have some badass shop tools with no truck to use them on. /forums/images/graemlins/thumb.gif