I was looking for a 130mm inner chainring to use on a friend's bike with 6-speed Shimano drivetrain (and fat early Uniglide chain). All of the 9- or 10-speed inner rings in my bin sit too close to the outer chainring. So I used a very worn-out 10-speed chainring (that someone had run with a chain that should have been replaced), and flipped it around. Clean side of the chainring teeth now pulling the chain, and the proper width away from the large ring. Nice when stuff like this works.