I didn't use it. I bought my car used and the guy before me ran a system. I found the hole he used and it already had a rubber gasket type thing.

This could be very nice to have in some installation scenarios, like a complete rebuild.

Just know that you don't want your power wire chaffing on the firewall.

Worked like a charm could be alittle stronger plastic but still a good product.

This is great for going thru the firewall. Keeps the wire safe and secure from grounding out.

This is the best grommet I have ever worked with. Seals up and locks down so the wire can not be pulled either way. Cost reflects the build quailty and performance. I have used this not only in automotive applications but also in marine applications which says alot for the performance.

This will allow you to go through the firewall without having to worry about grommets or the metal cutting the wire. Great Idea for a product!