Someone local is flogging this - It's not especially cheap, so I'd just like some advice on the quality? The main things I'm unsure on is what the lump on the side is, and if the metering valve is one of those choke ones, or a proper one. Also, I know these are really to be used with diesel compressors, but can you get any life from them with domestic units? (I've currently got 3-off giving, maybe, 35cfm ish - yeah, I know that's comparably nothing but would I be able to fit a smaller nozzle and still get some action?) Thank you.