Question about Thule EasyFold XT 3

The Easyfold XT F 3 is made exclusively for towballs with "FIX4BIKE", which is a special hitch that has a "tunnel" underneath the ball. Thanks to FIX4BIKE it's theoretically more stable and the bike carrier accepts a slightly higher weight.

In fact the one I ordered is foldable

Sorry, it's been too long, I can't remember the criteria, it seems to me that one model was foldable and the other one not. It's very nice to have a foldable one for storage.