We love our Cardo BK-1, same as the Terrano-X. I can use it on our triple with my 2 sons, as well as with my wife who would be riding on her single. Of course, we use it on our double tandem when we go out together.

I've found it is also nice when on singles and not needing to yell to communicate. It kills me when I see people riding 2 abreast so they can carry on a conversation when cars are whizzing by at 55 MPH with what I feel is not enough room. With the intercoms, you can still converse while riding in a safer configuration.