Coolant outlet. Get the aluminum one. Got mine from ZZP but it has been mentioned on the forum that it is cheaper elswhere, I think Amazon or Ebay Motors. The plastic wont last due to the coolant and high engine temps. I went through two before I found the aluminum one. https://www.sonicownersforum.com/forum/threads/aluminum-coolant-outlet-from-zzp.33185/
I wish someone would make an aluminum thermostat housing for the 1.4