This little thing does a much better job than the filter you receive from BT, O2, Virgin etc. at eliminating interferences. It's about 50% larger than a normal one, so that might account for the boost in performance.
The one I received was made by Belkin and came in Belkin packaging.
I tested the product the day I got it, using the following methodology:
-I used the normal Adsl filter that came with my O2 broadband and tested my internet's speed with
"http://top10.com/broadband/speedtest/" for 3(three) times over 10 minutes and worked out an average.
-Then I switched to the Belkin one and did the same thing.
The results showed an improvement from 6.7 mbps on the O2 one to 7.5 mbps on the Belkin one, using wireless and
an improvement from 14.4 mbps to 17.3 mbps when using a normal LAN cable.
The saying "Correlation is not causation" doesn't seem to stick here. The differences are too high for the results to be due to random chance.
So if you want faster, more reliable internet, you might consider investing into one of these.
Mind you though, your results might not necessarily replicate mine!
Hope this helps!