DO NOT buy the chinee knockoff GS911s. They may work for a while with the supplied software. Not so when you try to update, you won't be able to connect the knockoff to Hexcode and get the free updates.
If it comes with a disk, that's a knockoff. They just pirate the free software from Hexcode.
I played dumb with one of them sellers on fleabay.....as in ask dumb questions, had a good laugh at the answers.