All you need to do is place an expander ring onto the PEX pipe you want to use that's properly sized for the fitting you're aiming for, and then stick the tip of the expander tool into the opening.

If you’ve ever worked on plumbing, you might have heard of PEX. Milwaukee makes several PEX expander tools. Here is what they do and how to use them.

If you're working with PEX, you'll need an expander tool like DeWalt's. Here's exactly what the tool is and how you can expect it to work if you get one.