Whenever I have wanted to get some plug-ins for Photoshop or some great apps for my Mac they sometimes come in a “.sit” or a “.sitx” file. The reason being that “sit(x)” files are compressed making them more portable and accessible to others. The solution to opening these files is to download the freeware application Stuffit Expander. Stuffit Expander will open anything from a .sitx file to a .bin file. I highly recommend keeping this Mac app, as it will come in handy whenever you need to download something from the internet. Note: another application that opens up “sit(x)” files is The Unarchiver (freeware) — it works with more file-types and is open-source, which is one main reason I like The Unarchiver much better than Stuffit Expander.