Had to do a special project at work a few months back and thought I would share what I did. We had to run airlines in a part of the shop that didn't lend itself to being an easy job. Using the typical black iron pipe or copper was out of the question. So rather then do it my bosses way (who by the way claims to be smarter then everyone else) running 3/8"airline from Harbor Freight.... I opted for something a little more professional. I ran the entire job in Pex tubing. If your not familiar with Pex it is used mainly for plumbing and has pretty much replaced the old standard copper pipe. Especially on retrofits where you don't have to worry about burning the house down when sweating pipes. I invested his $100 in the better grade crimp tool that had a little LED indicator that lit up when the crimp was completed. The bottom line 9no pun intended) is we ran almost 300' of airline with a total of 12 speed couplers and another dozen or so connections for elbows T fittings etc. and not one single leak from the first time we fired it up to present. When we costed that part of the job out it was no more expensive then running either black pipe or copper lines. It may not be for you but if your looking for an alternative check with your local Lowes or Home Depot and compare prices.