I've had the Metallica Premium for a few years now. It needed to have the rubber rings replaced. So, I replaced them with silicon ones from Titan Pinball. I think the silicon ones look better, and I expect they will hold up better. I have these on the Avengers LE (blue) as well. I also expect the playfield will not be as dusty from the flakes of rubber. Let's see what happens.
Check the side by side photograph. I put the older rubber rings on the playfield to compare to the silicon ring on the kicker. You can see the rubber have a matte look to them. I am a big fan of the silicon rings. The rubber rings wear in a way that they shed tiny flakes of rubber. The ball picks them up and makes everything dirty. In theory, silicon rings wear better, last longer, and keep the machine clean.
Silicon rings are supposed to be as hard as the black rubber rings, no matter the color. With Rubber rings, black, red and white rubber can play significantly differently. I am not good enough to notice.
All in all, it took about 2-3 hours to go clockwise around the machine. I did it in two settings, and it's finally complete. Some are a pain. The rollovers were tough. I've fought these on the Wizard of Oz machine before.
So, it's in good shape. The playfield is clean, and the new silicone rings should last for a few years. I figured it was a good chance to take some photos of the rubber versus silicon. This way, I can check back in two years and see how the wear looks.