Having purchased a pack of these spoke reflectors one afternoon, they were delivered and installed on my bike the following morning! They simply clip, very snugly, to your spokes, and there is no movement on the spokes while in use. I was amazed at how light they are too. They must add a few grams at most to your bike when installed, less if you install on every other spoke as some other reviewers have suggested. While riding, I can honestly say that I felt no difference to the handling at all. It was like the reflectors weren't there. And, when night falls, they blaze brightly under any light source that catches them, transforming a turning wheel into a brilliant disc of solid light. As a driver, I find that reflective strips show cyclists more clearly at night than some lights and fluorescent coloured jackets. With these on my spokes, I'll feel much safer on my two-wheeled winter commutes.