Working with pnuematics and hydrolics you will at some point need to place a 45° or 90° fitting in a hard to reach place and these sockets have been a tremendous time saver for me. The ones I have are made by Snap-on but have seen them made by a couple of other companies and are called weatherhead sockets. I have a few machine parts I rebuild on the job that have a elbow fitting in a place that only allows a 1/4 turn with a wrench but with these sockets and an extension have a full 360° of motion and the ability to tighten down completely.