The narrow-wide chain ring is the one Trek sent and my LBS installed at no cost to me. The new chain was needed as I hammered the pedals when I thought I had got the chain back on the ring. Didn't work! It was 0400 and dark. I was in a rush to get to work. I think I was downshifting at the time. That was only the first time. I'm ready to get my money back and do something myself. Like a BBSHD. On a frame of my choice. Any ideas here? Thanks and Be Well, Bluesfrog.