.sitx File --- 7zip can't open it, what can?

I have a sitx archive. I think this is some MAC thing, but I need to open it in Windows.

7Zip doesn't recognize it.

What should I use?

From superuser

• It was created by Stuffit, there is a free expander program to extract it.

  http://stuffit-expander.en.softonic.com/mac