No matter what it is containing, a shut off valve is one of the most important elements of a piece of heavy machinery. As you can probably ascertain from its name, the valve serves to cease the flow of some substance through the apparatus. Because it serves such an importance purpose, it is important to invest in a quality part.
Stainless steel is always a good bet when it comes to machinery, and this is the case with a shut off valve too. You want to look for a model that has a manufacturer warranty and guarantee that backs up the performance of the product. While the part may be relatively small, the role that it plays in the operation of the machine is huge.