I used a clear silicone tube I purchased at home depot. Chose the higher heat application, so that there wouldn't be issues with a hot engine bay, lights, or warm weather. I actually applied the silicone on the outside of the headlight edges so that I could cut it off in the future (in case I needed to access the internals or repair the led rings).

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Current:
2008 BMW X5 3.0 Space Grey/ Tan
2009 Audi A4 2.0T Ibis White/Black
2017 Porsche Macan Black/ Garnet Red

Past:
2013 Mercedes C300 Palladium Silver/ Black-- sold & missed
2011 Buick Regal-- sold
2006 Jeep Liberty Limited White/ Grey -- RIP
2004 Jeep Liberty Limited Blue/ White-- RIP