3Easy: Let's start with the facts, there is nothing exciting about the design of this shroud. It's chrome. Its smooth. It's got no texture. No visual interest. No vents or holes for halos. It is the most utilitarian shroud known to retrofitting mankind, it's small, fit's in the tightest of spaces, and it's absolutely perfect [for that!] 3 Inch Projectors: If you've made the choice to shove a bigger projector with a 3 inch lens into something like your high beam reflector, and the projector just takes up all the available space to the point where no other shroud will fit, BOOM, that's where these come in handy. 99% of the time, these will be used in quad retrofits where the high beam position is way tight. Keep it tight: They sit nice and tight on a Morimoto Mini D2S 5.0 Bixenon projector, which is really what they were designed for. There is just a tiny vent on top for air flow, and a cutout on the bottom to just barely let the Bi-xenon solenoid poke through. Otherwise, they'll cover up the entire front half of the projector very well and add minimal extra size to the overall package. Mounting: These will press-fit directly onto the lens holder of a D2S 5.0 projector, no centric ring needed. You could use a centric ring to mount these on something smaller like a Mini H1, but there's really no point since the Mini Gatling Gun shroud is even smaller.