Using this with factory Audi crossbars, 2015 SQ5. carrying a 14' kayak, 40# before fishing gear. Components are durable, well thought out seem durable. Variable crossbar clamp styles, etc. One exception, the "red lever" tighter, both have blown off. Which becomes meaningless as the round bars require HUGE effort to move through clamps. Lithium grease, readjustment & alignment, no matter. Bad tolerances & clearances betweeen the components, they don't play well together. The potential opposite problem, round bars which slide too much, could easily be countered with stop collars and/or a meaningful "red lever" mechanism, or by using additional stop collars. The rails are extended by pulling the roller. With the tolerance issue noted above, it is a leverage chore, and I am 6'2". With anything other than perfect alignment and zero sliding resistance, the round bars pull unevenly and bind. In my case, one side of the roller pulls off. It is mounted by clamping a sleeve on the roller over the round rail. A better solution would be a "through pin" through the center of the outer sleeve going through the round bar. Once installed, the angles are fixed, and the three parts: round rails & roller, are an integrated unit. So, the pieces are well made, built for the task, a fine, tough, product. They just don't fit together well. Great concept, bad execution.