Can someone help me figure out what both of these LEGO part numbers are?
The first two pictures are the same brick at different angles to show it's strange design, while the third picture is the second brick, which also needs part identification.
As mentioned in another answer one part has two similar versions. Picture 3 shows the older 4081a and not the newer 4081b. This might be important, depending on your application. While both parts look to be very similar they have different properties. Older part has narrow/thin ring, which allows you to attach plates vertically on each side of the ring and such assembly won't be wider than the horizontal plate. Unfortunately, this doesn't work with newer part as ring is wider/ticker.