Let's discuss this because many people don't know a lot about these important parts. Everyone knows what they are but don't know which one to buy.
There's 5 types I know of: rubber, neoprene, polyurethane, aluminum with polyurithane, and solid aluminum. The rubber is traditional oem you can get this anywhere. neoprene is a bit harder and more durable you can get this at bavauto or other euro specialty sites. polyurethane is durable as well with different hardnesses 80d feels like stock blue color, 95d is harder for street and track (green color), and 75d is track only (orange color) I don't really know where these are but I have a friend with one, maybe they're custom made. Polyurethane with aluminum is the same deal as just polyurethane but I have one on my car and I noticed that many people don't torque these down. It's 30ft lbs then 60ft lbs, these are available at rev shift and I noticed that they need to be broken in daily, drive slow for the first 5-10 min of driving to stretch the polyurethane bushing. solid aluminum is only for track and you can't have more than .002 of an inch of run out so all new components every few months. I wish I had a go pro or camera because I'd also make a thread for installing my guibo I got at revshift.
