Electra's Seatpost Clamp w/Rack Mounts is the crucial link between your bike and your rear rack. It replaces the standard seatpost clamp to allow rack installation on bikes not originally fitted with rack eyelets.
I had to replace my adjustable seatpost clamp on my new bike to get a bike rack to fit. So I lost the "adjustability" of my seatpost, which I guess is ok, since I probably won't be adjusting it anyway. Still, I lost a feature of my bike, but at least I can fit a rack on now.
Bottom LineYes, I would recommend this to a friend