This was the worst value ever! The tour guide showed up 30 minutes late at the train station - and then took 3 minutes to advise how to get to Brussels and change trains and offered no other help. We were charged over 200 US dollars a piece and found out the train ticket was only 38 euros and the hop on hop off bus tour was only 25 Euros. When trying to voice my feedback - found out - can't get feedback to Viator. I use Viator all the time for my international travel and was very disappointed with this one. Complete rip off. Can't even give one STAR.
After meeting the tour representative at the train station, we were on our own boarding the train and having to change trains in Brussels to a commuter train. Once in Brussells we had to find our own way to the hop on/off bus. It was fairly easy to find, having been not far from the entrance.
There were two different routes for the bus tour with a total of 22 different stops. Depending on your interests there is a lot to see. We got lucky and found one of the touristy areas near the last few hours of the tour. The train to London didn't depart until around 6 or so at night, but the last hop on/off bus tour was at 4. If you missed the bus to take you back to the train station, you would have been on your own.
If you want an introductory tour to Brussells, I'd recommend this tour.