We have designed the easiest to install bulkhead you can get. just drill a 2 3/4 inch holes. This fitting sandwiches the metal, and protects your wiring from damage. no additional holes. It printed from a carbon fiber infused poly carbonate that has a very high heat resistance, but is also chemical and flane resistant. Custom sizes are also available by emailing firstname.lastname@example.org for anything custom. Everything is included to install except the hole saw.