This is one of four rubber grommets that were supplied with this servo. At first glace they may all appear identical (which they are) but the can be installed in the wrong orientation. If you look carefully you will notice that the top and bottom widths of the grommet are not the same. Remember that divider that I spoke of? The smaller width should go on top. If you put it in upside down the grommet will not sit correctly. It's easy to miss. I've seen many servos with the grommets install