yes, apparently a rotary oil filter? my guess is, it spins and pushes debris in the oil to the edge to accumulate? really I have no idea. like I said, this is just a spare engine that came with my 200X. clutch parts were in a box. someone over tightened clutch spring bolts and snapped them off. was just a little interested in getting it back together and seeing if it runs. was just a little stumped on what that part was.