Took the sm heads to a machine shop which was hard to find during the pandemic, still in the boxes to be checked and set up for my new cam choice. Paid them 1100$ to assure they were set up properly. Stock heads were worked before that by same shop. I explained that I wanted to use the lunati springs but when I picked them up, they were still on the stock heads. I told them they needed to be switched and asked them to leave the inner out for break in. The next day I went back and picked both sets of heads up. A year later when the car was painted, I was getting the valve train ready to put on action and noticed the dampers missing so I grabbed my compressor and started to install them. That's when I noticed the difference in size comparison to the sm heads original springs.