Firewall Feed-Thru Insulator

I know you said your going to wire it yourself but just wondering if you're going to use a kit? Like EZ wiring, or Painless. I know that my EZ wiring kit came with a round rubber insulator that you could pop into the metal plate that you made. I guess you know what I'm talking about. I might not be calling it what it truly should be called. It's like the rubber insulator that goes around the speedo cable through the firewall.