My friend bought a new Christmas tree stand and it didn't include the insert that screws to the bottom of the tree to help stabilize and align it. I printed one like the one that came with our stand - it's 200 mm in diameter and has countersink holes for two screws for the bottom of the tree trunk.

The collar mounts for the Tractive cat mini GPS trackers for our cats kept breaking so I finally created one. I got about 90% done with this model before looking on Makerworld and finding one from MrDownhouse which also works great but is a little bigger so I decided to continue with my version. Props to @MrDownhouse though for making me realize that the bumps help it keep from sliding on the collar. I'm no fusion pro but STL included, hope it helps someone out there.