Nipple, Heater Coolant Return @ Thermostat Housing.  Fits 90~95 ZR-1 LT5 engine. One (1) Coolant Return Nipple is required.  PN 10089613, Heater Return Tube Retainer is included.

Note: The original part was cast from pot metal which corroded and was easily broken off in the thermostat housing.  This upgraded design (same PN as original) is made from steel bar stock and incorporates the retainer latch groove internally as opposed to the "windows" in the original design.  Much better part.  Consider replacing your original while it is still intact and can be removed more easily.