Looks like a broken tree trunk and is also hollow. This log is closed at the top and has a small hole, which can turn the log into a cave for e.g. shrimps or small cichlids. The entrance hole is about 15 mm in diameter. Of course you can also use it to fix a plant there.
This part is in the bargain corner because it is a single piece of a discontinued idea/model series. Without defects.
Height approx. 8 cm
Ø inside approx. 3 cm