Nah, they were packed with the H20's for future (Mpeg4) use... The B-Band converter is used with the AT9 to pass the Ka-LO band (250-750MHz) signals...see This Thread
its a filter which allows you to view mpeg4 hd broadcasts on either the h20 or hr20!! both of mine came with the filters in the box. but evidently not everybody has the filter. if you have either and/or both of those units, without filters......you can request from d*!
They are only for the H20 and HR20. They will convert the B-Band Ka LNB output (250-750 MHz) to A-Band (1650-2150 MHz) for use with the Directv 10 and 11 satellites. They come with the receivers, but since they aren't yet required it seems that some installers aren't giving them to the customers or the customers are losing them, hence the link to an order page. They won't do any magic for a H10 or other models.
I can remember the installer coming to the house and installing the filter then when I had issues with NESN HD they took the filter off. (obviously the filter had nothing to do with it.)