You don't see too many that don't attach directly to the spindle or router if that is what you mean. I don't remember the site, but there are a couple of versions that mount to the Z axis base (where it mounts to the gantry) with 2 rods, and you can set the boot height with thump screws. A little searching on the web or you tube should locate them. On those of this design I have seen, the spindle goes up and down within the boot. These designs may work with a very good vacuum system, but the more "gaps" that allow air to flow from other than directly under the spindle the less efficient the vacuum is.