This is the proper insulator for the top or bottom of the Gen2 or Gen3 3SGTE fuel injectors. These are not the sealing o-rings, but are the vibration insulators that go at the top and bottom of the injector to help locate it in the fuel rail.
NOTE: You are purchasing ONE PAIR of insulators, or enough for ONE fuel injector. If you are replacing all of your insulators, you will need to order a quantity of 4 (four).