I am looking at the internal area, so where the equipment would actually slide into. The 7700 is 17.2 and the 7125 is 17.25. On the Omnimount sheet, it says it is 17.2. SO that is why I am not sure if maybe Outlaw's numbers are off a bit, or Omnimount or what. I just don't want to buy it, then one or more things don't fit.