The following mold variations of part 3660 have been found so far:
The stud holes look bar-sized but they are still slightly smaller and do not allow inserting bars.
Types 1, 2, 4, 5 are shown in the photo below:
Type 3 is shown in the photos by biodreamer.
Click on a colored part below to see the Sets and MOCs that use part 3660 Slope Inverted 45° 2 x 2 [Ovoid Bottom Pin, Bar-sized Stud Holes] in that color. You can find an overview of all LEGO Colors here.
If a color is missing, it probably needs to be added to a Set Inventory.
This part has been used by MOCs in the following colors but not officially released.