I've got one on my Yamaha 1100 Virago. Best $36.00 I ever spent. It really helps to eliminate "wrist fatique"
I don't know it it will fit a Harley or not. I'm planning on renting a RoadKing in June for a week long trip in the Rockies so I went to my local Hog dealer yesterday to see and sit on a Roadking. First thing I noticed is that there doesn't appear to be enough room to install the Vistacruise on the stock handlebar although I would have to measure it to make sure. If anyone has installed a Vistacruise on a late model RoadKing, please let me know 'cause I would buy one just to use for a week.
Second thing I noticed is that the stock RoadKing seat is HARD!! Maybe my butt is too use to the soft Yamaha seat, but I immediately ordered a gel pad to take with me. I sure hope the gel pad works 'cause the last thing I want is to spend seven days on the road with a sore butt!!