Priceless: These allow use of the most common shrouds with 3" openings to fit a 2.5" projector beautifully. Installation: Snaps into the circular flange on the backside of the shrouds, and fits tight over the front lens frame of the projectors for a perfect fit. NOTE: We do recommend adding epoxy/silicone in between surfaces to ensure vibration never shakes them loose. Yes their friction-fit is tight, but better safe than sorry! NOTE: Will not fit E46-R or Gatling Gun 2.0 shrouds without modification. Free: Included at no charge when you order both premium shrouds and a set of compatible projectors from our shop for simple, instant, and effective mounting.