First, it's really hard to determine how high your ceiling needs to be in order to use this.  If you have an older home like I do, with 8 ft ceilings, don't bother unless you have a place to put it that you don't have to walk under.  Second, the thing is absolute rubbish.  The grate doesn't stay in place, and the brackets that come together at the top don't meet up cleanly, no matter what you try.