We designed this cap to be a superior alternative to the OEM end caps, which are very easily broken. They screw on to the end like the factory one, but are made of a much thicker and stronger ABS plastic. And, they glow in the dark after being exposed to light. The plastic is transluscent so the turn signal is bright. We are so confident you will like these more we offer a lifetime warranty. If you ever break them in a bad crash, just send them back for a fast replacement. Made in Seattle, USA!