Bought these for my old dulcimer as it had hand carved wood pegs that always slipped or tuned with difficulty. Took these out of the package and slipped them right into the tuning peg holes - no extra work required. They have four slight ribs to hold them in place, but not enough that they will damage the original peg hole, so the old pegs can work again. Once in place, I setup the strings and played music within an hour of opening the package. They do crank slowly, which is a pain during setup, but the positive thing is that gives them more torque to hold and finer tuning capability. Use a tuning peg crank if you need. I will buy these for my violins eventually. What a great product!