I'm not sure you even need to remove the heat sync tbh.
I noticed on my bulbs there was a plastic bit that the bulb effectively screws into, but it looks like part of the stem of the bulb.
Excuse the shoddy screeny and explanation, but...
The bit in the circle is like the retainer metal on a normal bulb, but it screws off these LEDs and then you put that into the car's bulb slot, apply the retainer clip to hold it in place as you would a regular sized bulb, then finally screw the LED back into the plastic retainer.
Hopefully that makes sense?
Took me ages figuring out, how the F can the retainer clip fit over the LEDs fat backside?
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You're not leaving the heat sink off are you??