has any one ever installed and or used them?? do they work.a buddy of mine has them on his bow and raves about them . thanks for any info.

I have heard that they work, but they only add like 5fps or soI think. For me it's not worth it.

Depending on the setup they can work, but it takes a lot of experimentation. You have to put one on, shoot through a crono and compare it to other crono readings with it in a different spot. A pain in the butt and a complete waste of time, since a couple fps is so totally meaningless.

Yup.