I made this section out of 1" threaded steel pipe. I used several wraps of teflon tape at each joint to prevent leaks. I had to use a bunch of adapters, etc., which are mostly based on what home depot had when I was there.
The pipe goes into a male cleanout cap at one end, where I screwed on a female coupler to act as a nut, and on the out side, I use a piece of thin pipe, so the nut has something to push against. There is a large steel washer, a piece of neoprene, and an O-ring which help keep it airtight. I used some parts of an old foam camping mattress in the clean out cap to act as a bumper for the piston.
There is an electronic sprinkler vavle that lets the air out the back, which in turns lets the piston move back, I have replaced it with a manual ball valve for now, because it is simpler. I may replace it later when everything else is squared away.
I have a pressure gauge that is attached via a piece of red hose, this is to help protect it from pressure shock,(I have also heard that this is not necessary, but I am being on the safe side). There is a small ball valve where the compressor hooks up, which is just for convenience.