Quick question about ka24de reassembly ($5 amazon gift card if you help me)

[Bovilla]

I have my head off and about to put new timing chain and headgasket. Looking through the nuts/bolts I have taken off I found a small metal cylinder that I forgot to label. Looks like an insert of some sort between oil or coolant passages. It is smaller in size then the two inserts going between the head and block. Any ideas? I wanna make sure it goes in the right spot.