One of the local high school x country ski team trains on my street with roller skis. It is frightening! The street is an almost 2 mile loop that looks like the number 9. The beginning of the street, the tail of the 9 is a 10% grade and one side of the loop is about 8-10%. Then it goes down and rises up again before the descent back down. I don't know how these people do this, without brakes on those things . They certainly look fit, but I would go for the ones with the brakes.