No problems installing on a 1995 Corolla. It was neat to remove and install due to the aluminum body and small studs. I used a thermostat o-ring from a local store and the parts store says they also use a traditional flange gasket, although it wasn't shown in the installation videos, just an o-ring. Went with both and no leaks and bad interior heater seems fixed. I wanted O-rings or flange gaskets to be included, but I knew from the order description that this was not the case.