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: This 10 pack will cover one complete set of 4 injectors with 2 left over (just in case one rolls under the tool box or gets damaged).