We have fitment categories in the Slingshot app, and we have fitment buckets in the Turn 14 app. They are both the same tool, we just updated the name! If you have both apps installed and you want to create fitment based collections with both apps, they will share the same collections as long as you use the exact same title in both app.
For example if I have both apps installed and I want one fitment based collection for Ford Bronco from 2021-2024 I would create the same title in both the Turn 14 app buckets, and the slingshot fitment categories. Then I would set the same fitment of Ford Bronco 2021-2024 and save. Then I would get one collection with products from both apps!