Hmm interesting I don't recall this bolt. I will need to take a look whenever I replace the factory speakers.Yes, install is finished. It was a long road getting it working. The problem wasn't the head unit as first thought. Long story short, there's a pair of ground wires behind the back seat upright, the bolt securing them was loose. It's now fixed and we're very happy with the new system. Didn't need the isolators.