This is a replacement "screw drive coupling" for certain LiftMaster and other garage door openers. According to the LiftMaster site it's a replacement for part numbers the following part numbers: K025C0020, 025A0018, 025A0020, 025C0020.
New ones are available for cheap from LiftMaster or Amazon but I needed one right away and the shipping was going to take too long.
I printed mine with 100% infill and have been using it for 5 days with no problems so far.