What Bob said. It's a very simple installation and done correctly will last indefinitely. And you can adjust them up and down the serving like a nut on a bolt---and they don't move on their own. There is also the added feature that you'll gain some speed. I've chrono'd the results on my bow and found that a brass nockset robs my bow of 4fps. So if you're one of those guys that has a double above the arrow and one below you've just cheated yourself out of 12fps.